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NAME | OVERVIEW OF THE ABIGAIL FRAMEWORK | TOOLS | CONCEPTS | AUTHOR | COPYRIGHT | COLOPHON |
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LIBABIGAIL(7) Libabigail LIBABIGAIL(7)
libabigail - Library to analyze and compare ELF ABIs
ABIGAIL stands for the Application Binary Interface Generic
Analysis and Instrumentation Library.
It's a framework which aims at helping developers and software
distributors to spot some ABI-related issues like interface
incompatibility in ELF shared libraries by performing a static
analysis of the ELF binaries at hand.
The type of interface incompatibilities that Abigail focuses on
is related to changes on the exported ELF functions and variables
symbols, as well as layout and size changes of data types of the
functions and variables exported by shared libraries.
In other words, if the return type of a function exported by a
shared library changes in an incompatible way from one version of
a given shared library to another, we want Abigail to help people
catch that.
In more concrete terms, the Abigail framwork provides a shared
library named libabigail which exposes an API to parse a shared
library in ELF format (accompanied with its associated debug
information in DWARF format) build an internal representation of
all the functions and variables it exports, along with their
types. Libabigail also builds an internal representation of the
ELF symbols of these functions and variables. That information
about these exported functions and variables is roughly what we
consider as being the ABI of the shared library, at least, in the
scope of Libabigail.
Aside of this internal representation, libabigail provides
facilities to perform deep comparisons of two ABIs. That is, it
can compare the types of two sets of functions or variables and
represents the result in a way that allows it to emit textual
reports about the differences.
This allows us to write tools like abidiff that can compare the
ABI of two shared libraries and represent the result in a
meaningful enough way to help us spot ABI incompatibilities.
There are several other tools that are built using the Abigail
framwork.
Overview
The upstream code repository of Libabigail contains several tools
written using the library. They are maintained and released as
part of the project. All tools come with a bash-completion
script.
Tools manuals
abidiff
abidiff compares the Application Binary Interfaces (ABI) of two
shared libraries in ELF format. It emits a meaningful report
describing the differences between the two ABIs.
This tool can also compare the textual representations of the ABI
of two ELF binaries (as emitted by abidw) or an ELF binary
against a textual representation of another ELF binary.
For a comprehensive ABI change report between two input shared
libraries that includes changes about function and variable
sub-types, abidiff uses by default, debug information in DWARF
format, if present, otherwise it compares interfaces using debug
information in CTF or BTF formats, if present. Finally, if no
debug info in these formats is found, it only considers ELF
symbols and report about their addition or removal.
This tool uses the libabigail library to analyze the binary as
well as its associated debug information. Here is its general
mode of operation.
When instructed to do so, a binary and its associated debug
information is read and analyzed. To that effect, libabigail
analyzes by default the descriptions of the types reachable by
the interfaces (functions and variables) that are visible outside
of their translation unit. Once that analysis is done, an
Application Binary Interface Corpus is constructed by only
considering the subset of types reachable from interfaces
associated to ELF symbols that are defined and exported by the
binary. It's that final ABI corpus which libabigail considers as
representing the ABI of the analyzed binary.
Libabigail then has capabilities to generate textual
representations of ABI Corpora, compare them, analyze their
changes and report about them.
Invocation
abidiff [options] <first-shared-library> <second-shared-library>
Environment
abidiff loads two default suppression specifications files,
merges their content and use it to filter out ABI change reports
that might be considered as false positives to users.
• Default system-wide suppression specification file
It's located by the optional environment variable
LIBABIGAIL_DEFAULT_SYSTEM_SUPPRESSION_FILE. If that
environment variable is not set, then abidiff tries to load the
suppression file
$libdir/libabigail/libabigail-default.abignore. If that file
is not present, then no default system-wide suppression
specification file is loaded.
• Default user suppression specification file.
It's located by the optional environment
LIBABIGAIL_DEFAULT_USER_SUPPRESSION_FILE. If that environment
variable is not set, then abidiff tries to load the suppression
file $HOME/.abignore. If that file is not present, then no
default user suppression specification is loaded.
Options
• --help | -h
Display a short help about the command and exit.
• --debug-self-comparison
In this mode, error messages are emitted for types which
fail type canonicalization, in some circumstances, when
comparing a binary against itself.
When comparing a binary against itself, canonical types of
the second binary should be equal (as much as possible) to
canonical types of the first binary. When some
discrepancies are detected in this mode, an abort signal is
emitted and execution is halted. This option should be used
while executing the tool in a debugger, for troubleshooting
purposes.
This is an optional debugging and sanity check option. To
enable it the libabigail package needs to be configured with
the --enable-debug-self-comparison configure option.
• --debug-tc
In this mode, the process of type canonicalization is put
under heavy scrutiny. Basically, during type
canonicalization, each type comparison is performed twice:
once in a structural mode (comparing every sub-type
member-wise), and once using canonical comparison. The two
comparisons should yield the same result. Otherwise, an
abort signal is emitted and the process can be debugged to
understand why the two kinds of comparison yield different
results.
This is an optional debugging and sanity check option. To
enable it the libabigail package needs to be configured with
the --enable-debug-type-canonicalization configure option.
• --version | -v
Display the version of the program and exit.
• --debug-info-dir1 | --d1 <di-path1>
For cases where the debug information for
first-shared-library is split out into a separate file,
tells abidiff where to find that separate debug information
file.
Note that di-path must point to the root directory under
which the debug information is arranged in a tree-like
manner. Under Red Hat based systems, that directory is
usually <root>/usr/lib/debug.
This option can be provided several times with different
root directories. In that case, abidiff will potentially
look into all those root directories to find the split debug
info for first-shared-library.
Note also that this option is not mandatory for split debug
information installed by your system's package manager
because then abidiff knows where to find it.
• --debug-info-dir2 | --d2 <di-path2>
Like --debug-info-dir1, this options tells abidiff where to
find the split debug information for the
second-shared-library file.
This option can be provided several times with different
root directories. In that case, abidiff will potentially
look into all those root directories to find the split debug
info for second-shared-library.
• --headers-dir1 | --hd1 <headers-directory-path-1>
Specifies where to find the public headers of the first
shared library (or binary in general) that the tool has to
consider. The tool will thus filter out ABI changes on
types that are not defined in public headers.
Note that several public header directories can be specified
for the first shared library. In that case the
--headers-dir1 option should be present several times on the
command line, like in the following example:
$ abidiff --headers-dir1 /some/path \
--headers-dir1 /some/other/path \
binary-version-1 binary-version-2
• --header-file1 | --hf1 <header-file-path-1>
Specifies where to find one public header of the first
shared library that the tool has to consider. The tool will
thus filter out ABI changes on types that are not defined in
public headers.
• --headers-dir2 | --hd2 <headers-directory-path-2>
Specifies where to find the public headers of the second
shared library that the tool has to consider. The tool will
thus filter out ABI changes on types that are not defined in
public headers.
Note that several public header directories can be specified
for the second shared library. In that case the
--headers-dir2 option should be present several times like
in the following example:
$ abidiff --headers-dir2 /some/path \
--headers-dir2 /some/other/path \
binary-version-1 binary-version-2
• --header-file2 | --hf2 <header-file-path-2>
Specifies where to find one public header of the second
shared library that the tool has to consider. The tool will
thus filter out ABI changes on types that are not defined in
public headers.
• --add-binaries1 <bin1,bin2,bin3,..>
For each of the comma-separated binaries given in argument
to this option, if the binary is found in the directory
specified by the --added-binaries-dir1 option, then abidiff
loads the ABI corpus of the binary and adds it to a set of
corpora (called an ABI Corpus Group) that includes the first
argument of abidiff.
That ABI corpus group is then compared against the second
corpus group given in argument to abidiff.
• --add-binaries2 <bin1,bin2,bin3,..>
For each of the comma-separated binaries given in argument
to this option, if the binary is found in the directory
specified by the --added-binaries-dir2 option, then abidiff
loads the ABI corpus of the binary and adds it to a set of
corpora(called an ABI Corpus Group) that includes the second
argument of abidiff.
That ABI corpus group is then compared against the first
corpus group given in argument to abidiff.
• --follow-dependencies | --fdeps
For each dependency of the first argument of abidiff, if
it's found in the directory specified by the
--added-binaries-dir1 option, then construct an ABI corpus
out of the dependency, add it to a set of corpora (called an
ABI Corpus Group) that includes the first argument of
abidiff.
Similarly, for each dependency of the second argument of
abidiff, if it's found in the directory specified by the
--added-binaries-dir2 option, then construct an ABI corpus
out of the dependency, add it to an ABI corpus group that
includes the second argument of abidiff.
These two ABI corpus groups are then compared against each
other.
Said otherwise, this makes abidiff compare the set of its
first input and its dependencies against the set of its
second input and its dependencies.
• list-dependencies | --ldeps
This option lists all the dependencies of the input
arguments of abidiff that are found in the directories
specified by the options --added-binaries-dir1 and
--added-binaries-dir2
• --added-binaries-dir1 | --abd1 <added-binaries-directory-1>
This option is to be used in conjunction with the
--add-binaries1, --follow-dependencies and
--list-dependencies options. Binaries referred to by these
options, if found in the directory
added-binaries-directory-1, are loaded as ABI corpus and are
added to the first ABI corpus group that is to be used in
the comparison.
• --added-binaries-dir2 | --abd2 <added-binaries-directory-2>
This option is to be used in conjunction with the
--add-binaries2, --follow-dependencies and
--list-dependencies options. Binaries referred to by these
options, if found in the directory
added-binaries-directory-2, are loaded as ABI corpus and are
added to the second ABI corpus group to be used in the
comparison.
• --no-linux-kernel-mode
Without this option, if abidiff detects that the binaries it
is looking at are Linux Kernel binaries (either vmlinux or
modules) then it only considers functions and variables
which ELF symbols are listed in the __ksymtab and
__ksymtab_gpl sections.
With this option, abidiff considers the binary as a
non-special ELF binary. It thus considers functions and
variables which are defined and exported in the ELF sense.
• --kmi-whitelist | -kaw <path-to-whitelist>
When analyzing a Linux kernel binary, this option points to
the white list of names of ELF symbols of functions and
variables which ABI must be considered. That white list is
called a "Kernel Module Interface white list". This is
because for the Kernel, we don't talk about ABI; we rather
talk about the interface between the Kernel and its module.
Hence the term KMI rather than ABI.
Any other function or variable which ELF symbol are not
present in that white list will not be considered by this
tool.
If this option is not provided -- thus if no white list is
provided -- then the entire KMI, that is, the set of all
publicly defined and exported functions and global variables
by the Linux Kernel binaries, is considered.
• --drop-private-types
This option is to be used with the --headers-dir1,
header-file1, header-file2 and --headers-dir2 options. With
this option, types that are NOT defined in the headers are
entirely dropped from the internal representation build by
Libabigail to represent the ABI. They thus don't have to be
filtered out from the final ABI change report because they
are not even present in Libabigail's representation.
Without this option however, those private types are kept in
the internal representation and later filtered out from the
report.
This options thus potentially makes Libabigail consume less
memory. It's meant to be mainly used to optimize the memory
consumption of the tool on binaries with a lot of publicly
defined and exported types.
• --exported-interfaces-only
By default, when looking at the debug information
accompanying a binary, this tool analyzes the descriptions
of the types reachable by the interfaces (functions and
variables) that are visible outside of their translation
unit. Once that analysis is done, an ABI corpus is
constructed by only considering the subset of types
reachable from interfaces associated to ELF symbols that are
defined and exported by the binary. It's those final ABI
Corpora that are compared by this tool.
The problem with that approach however is that analyzing all
the interfaces that are visible from outside their
translation unit can amount to a lot of data, especially
when those binaries are applications, as opposed to shared
libraries. One example of such applications is the Linux
Kernel. Analyzing massive ABI corpora like these can be
extremely slow.
To mitigate that performance issue, this option allows
libabigail to only analyze types that are reachable from
interfaces associated with defined and exported ELF symbols.
Note that this option is turned on by default when analyzing
the Linux Kernel. Otherwise, it's turned off by default.
• --allow-non-exported-interfaces
When looking at the debug information accompanying a binary,
this tool analyzes the descriptions of the types reachable
by the interfaces (functions and variables) that are visible
outside of their translation unit. Once that analysis is
done, an ABI corpus is constructed by only considering the
subset of types reachable from interfaces associated to ELF
symbols that are defined and exported by the binary. It's
those final ABI Corpora that are compared by this tool.
The problem with that approach however is that analyzing all
the interfaces that are visible from outside their
translation unit can amount to a lot of data, especially
when those binaries are applications, as opposed to shared
libraries. One example of such applications is the Linux
Kernel. Analyzing massive ABI Corpora like these can be
extremely slow.
In the presence of an "average sized" binary however one can
afford having libabigail analyze all interfaces that are
visible outside of their translation unit, using this
option.
Note that this option is turned on by default, unless we are
in the presence of the Linux Kernel.
• --stat
Rather than displaying the detailed ABI differences between
first-shared-library and second-shared-library, just display
some summary statistics about these differences.
• --symtabs
Only display the symbol tables of the first-shared-library
and second-shared-library.
• --deleted-fns
In the resulting report about the differences between
first-shared-library and second-shared-library, only display
the globally defined functions that got deleted from
first-shared-library.
• --changed-fns
In the resulting report about the differences between
first-shared-library and second-shared-library, only display
the changes in sub-types of the global functions defined in
first-shared-library.
• --added-fns
In the resulting report about the differences between
first-shared-library and second-shared-library, only display
the globally defined functions that were added to
second-shared-library.
• --deleted-vars
In the resulting report about the differences between
first-shared-library and second-shared-library, only display
the globally defined variables that were deleted from
first-shared-library.
• --changed-vars
In the resulting report about the differences between
first-shared-library and second-shared-library, only display
the changes in the sub-types of the global variables defined
in first-shared-library
• --added-vars
In the resulting report about the differences between
first-shared-library and second-shared-library, only display
the global variables that were added (defined) to
second-shared-library.
• --non-reachable-types|-t
Analyze and emit change reports for all the types of the
binary, including those that are not reachable from global
functions and variables.
This option might incur some serious performance degradation
as the number of types analyzed can be huge. However, if
paired with the --headers-dir{1,2} and/or header-file{1,2}
options, the additional non-reachable types analyzed are
restricted to those defined in public headers files, thus
hopefully making the performance hit acceptable.
Also, using this option alongside suppression specifications
(by also using the --suppressions option) might help keep
the number of analyzed types (and the potential performance
degradation) in control.
Note that without this option, only types that are reachable
from global functions and variables are analyzed, so the
tool detects and reports changes on these reachable types
only.
• --no-added-syms
In the resulting report about the differences between
first-shared-library and second-shared-library, do not
display added functions or variables. Do not display added
functions or variables ELF symbols either. All other kinds
of changes are displayed unless they are explicitely
forbidden by other options on the command line.
• --no-linkage-name
In the resulting report, do not display the linkage names of
the added, removed, or changed functions or variables.
• --no-show-locs
Do not show information about where in the second shared
library the respective type was changed.
• --show-bytes
Show sizes and offsets in bytes, not bits. By default,
sizes and offsets are shown in bits.
• --show-bits
Show sizes and offsets in bits, not bytes. This option is
activated by default.
• --show-hex
Show sizes and offsets in hexadecimal base.
• --show-dec
Show sizes and offsets in decimal base. This option is
activated by default.
• --ignore-soname
Ignore differences in the SONAME when doing a comparison
• --no-show-relative-offset-changes
Without this option, when the offset of a data member
changes, the change report not only mentions the older and
newer offset, but it also mentions by how many bits the data
member changes. With this option, the latter is not shown.
• --no-unreferenced-symbols
In the resulting report, do not display change information
about function and variable symbols that are not referenced
by any debug information. Note that for these symbols not
referenced by any debug information, the change information
displayed is either added or removed symbols.
• --no-default-suppression
Do not load the default suppression specification files.
• --suppressions | --suppr <path-to-suppressions>
Use a suppression specification file located at
path-to-suppressions. Note that this option can appear
multiple times on the command line. In that case, all of
the provided suppression specification files are taken into
account.
Please note that, by default, if this option is not
provided, then the default suppression specification files
are loaded .
• --drop <regex>
When reading the first-shared-library and
second-shared-library ELF input files, drop the globally
defined functions and variables which name match the regular
expression regex. As a result, no change involving these
functions or variables will be emitted in the diff report.
• --drop-fn <regex>
When reading the first-shared-library and
second-shared-library ELF input files, drop the globally
defined functions which name match the regular expression
regex. As a result, no change involving these functions
will be emitted in the diff report.
• --drop-var <regex>
When reading the first-shared-library and
second-shared-library ELF input files, drop the globally
defined variables matching a the regular expression regex.
• --keep <regex>
When reading the first-shared-library and
second-shared-library ELF input files, keep the globally
defined functions and variables which names match the
regular expression regex. All other functions and variables
are dropped on the floor and will thus not appear in the
resulting diff report.
• --keep-fn <regex>
When reading the first-shared-library and
second-shared-library ELF input files, keep the globally
defined functions which name match the regular expression
regex. All other functions are dropped on the floor and
will thus not appear in the resulting diff report.
• --keep-var <regex>
When reading the first-shared-library and
second-shared-library ELF input files, keep the globally
defined which names match the regular expression regex. All
other variables are dropped on the floor and will thus not
appear in the resulting diff report.
• --harmless
In the diff report, display only the harmless changes. By
default, the harmless changes are filtered out of the diff
report keep the clutter to a minimum and have a greater
chance to spot real ABI issues.
• --no-harmful
In the diff report, do not display the harmful changes. By
default, only the harmful changes are displayed in diff
report.
• --redundant
In the diff report, do display redundant changes. A
redundant change is a change that has been displayed
elsewhere in the report.
• --no-redundant
In the diff report, do NOT display redundant changes. A
redundant change is a change that has been displayed
elsewhere in the report. This option is switched on by
default.
• --no-architecture
Do not take architecture in account when comparing ABIs.
• --no-corpus-path
Do not emit the path attribute for the ABI corpus.
• --fail-no-debug-info
If no debug info was found, then this option makes the
program to fail. Otherwise, without this option, the
program will attempt to compare properties of the binaries
that are not related to debug info, like pure ELF
properties.
• --leaf-changes-only|-l only show leaf changes, so don't show
impact analysis report. This option implies --redundant.
The typical output of abidiff when comparing two binaries
looks like this
$ abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void fn(C&)' at test-v1.cc:13:1 has some indirect sub-type changes:
parameter 1 of type 'C&' has sub-type changes:
in referenced type 'struct C' at test-v1.cc:7:1:
type size hasn't changed
1 data member change:
type of 'leaf* C::m0' changed:
in pointed to type 'struct leaf' at test-v1.cc:1:1:
type size changed from 32 to 64 bits
1 data member insertion:
'char leaf::m1', at offset 32 (in bits) at test-v1.cc:4:1
$
So in that example the report emits information about how
the data member insertion change of "struct leaf" is
reachable from function "void fn(C&)". In other words, the
report not only shows the data member change on "struct
leaf", but it also shows the impact of that change on the
function "void fn(C&)".
In abidiff parlance, the change on "struct leaf" is called a
leaf change. So the --leaf-changes-only
--impacted-interfaces options show, well, only the leaf
change. And it goes like this:
$ abidiff -l libtest-v0.so libtest-v1.so
'struct leaf' changed:
type size changed from 32 to 64 bits
1 data member insertion:
'char leaf::m1', at offset 32 (in bits) at test-v1.cc:4:1
one impacted interface:
function void fn(C&)
$
Note how the report ends by showing the list of interfaces
impacted by the leaf change.
Now if you don't want to see that list of impacted
interfaces, then you can just avoid using the
--impacted-interface option. You can learn about that
option below, in any case.
• --impacted-interfaces
When showing leaf changes, this option instructs abidiff to
show the list of impacted interfaces. This option is thus
to be used in addition the --leaf-changes-only option,
otherwise, it's ignored.
• --dump-diff-tree
After the diff report, emit a textual representation of
the diff nodes tree used by the comparison engine to
represent the changed functions and variables. That
representation is emitted to the error output for
debugging purposes. Note that this diff tree is relevant
only to functions and variables that have some sub-type
changes. Added or removed functions and variables do not
have any diff nodes tree associated to them.
• --no-assume-odr-for-cplusplus
When analysing a binary originating from C++ code using
DWARF debug information, libabigail assumes the One
Definition Rule to speed-up the analysis. In that case,
when several types have the same name in the binary, they
are assumed to all be equal.
This option disables that assumption and instructs
libabigail to actually actually compare the types to
determine if they are equal.
• --no-leverage-dwarf-factorization
When analysing a binary which DWARF debug information was
processed with the DWZ tool, the type information is
supposed to be already factorized. That context is used by
libabigail to perform some speed optimizations.
This option disables those optimizations.
• --no-change-categorization | -x
This option disables the categorization of changes into
harmless and harmful changes. Note that this categorization
is a pre-requisite for the filtering of changes so this
option disables that filtering. The goal of this option is
to speed-up the execution of the program for cases where the
graph of changes is huge and where the user is just
interested in looking at, for instance, leaf node changes
without caring about their possible impact on interfaces.
In that case, this option would be used along with the
--leaf-changes-only one.
• --ctf
When comparing binaries, extract ABI information from CTF
debug information, if present.
• --btf
When comparing binaries, extract ABI information from BTF
debug information, if present.
• --stats
Emit statistics about various internal things.
• --verbose
Emit verbose logs about the progress of miscellaneous
internal things.
Return values
The exit code of the abidiff command is either 0 if the ABI of
the binaries being compared are equal, or non-zero if they differ
or if the tool encountered an error.
In the later case, the exit code is a 8-bits-wide bit field in
which each bit has a specific meaning.
The first bit, of value 1, named ABIDIFF_ERROR means there was an
error.
The second bit, of value 2, named ABIDIFF_USAGE_ERROR means there
was an error in the way the user invoked the tool. It might be
set, for instance, if the user invoked the tool with an unknown
command line switch, with a wrong number or argument, etc. If
this bit is set, then the ABIDIFF_ERROR bit must be set as well.
The third bit, of value 4, named ABIDIFF_ABI_CHANGE means the ABI
of the binaries being compared are different.
The fourth bit, of value 8, named ABIDIFF_ABI_INCOMPATIBLE_CHANGE
means the ABI of the binaries compared are different in an
incompatible way. If this bit is set, then the
ABIDIFF_ABI_CHANGE bit must be set as well. If the
ABIDIFF_ABI_CHANGE is set and the ABIDIFF_INCOMPATIBLE_CHANGE is
NOT set, then it means that the ABIs being compared might or
might not be compatible. In that case, a human being needs to
review the ABI changes to decide if they are compatible or not.
Note that, at the moment, there are only a few kinds of ABI
changes that would result in setting the flag
ABIDIFF_ABI_INCOMPATIBLE_CHANGE. Those ABI changes are either:
• the removal of the symbol of a function or variable that has
been defined and exported.
• the modification of the index of a member of a virtual
function table (for C++ programs and libraries).
With time, when more ABI change patterns are found to always
constitute incompatible ABI changes, we will adapt the code to
recognize those cases and set the ABIDIFF_ABI_INCOMPATIBLE_CHANGE
accordingly. So, if you find such patterns, please let us know.
The remaining bits are not used for the moment.
Usage examples
1. Detecting a change in a sub-type of a function:
$ cat -n test-v0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
3
4 struct S0
5 {
6 int m0;
7 };
8
9 void
10 foo(S0* /*parameter_name*/)
11 {
12 // do something with parameter_name.
13 }
$
$ cat -n test-v1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
3
4 struct type_base
5 {
6 int inserted;
7 };
8
9 struct S0 : public type_base
10 {
11 int m0;
12 };
13
14 void
15 foo(S0* /*parameter_name*/)
16 {
17 // do something with parameter_name.
18 }
$
$ g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
$ g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
$
$ ../build/tools/abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void foo(S0*)' has some indirect sub-type changes:
parameter 0 of type 'S0*' has sub-type changes:
in pointed to type 'struct S0':
size changed from 32 to 64 bits
1 base class insertion:
struct type_base
1 data member change:
'int S0::m0' offset changed from 0 to 32
$
2. Detecting another change in a sub-type of a function:
$ cat -n test-v0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
3
4 struct S0
5 {
6 int m0;
7 };
8
9 void
10 foo(S0& /*parameter_name*/)
11 {
12 // do something with parameter_name.
13 }
$
$ cat -n test-v1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
3
4 struct S0
5 {
6 char inserted_member;
7 int m0;
8 };
9
10 void
11 foo(S0& /*parameter_name*/)
12 {
13 // do something with parameter_name.
14 }
$
$ g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
$ g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
$
$ ../build/tools/abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void foo(S0&)' has some indirect sub-type changes:
parameter 0 of type 'S0&' has sub-type changes:
in referenced type 'struct S0':
size changed from 32 to 64 bits
1 data member insertion:
'char S0::inserted_member', at offset 0 (in bits)
1 data member change:
'int S0::m0' offset changed from 0 to 32
$
3. Detecting that functions got removed or added to a library:
$ cat -n test-v0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
3
4 struct S0
5 {
6 int m0;
7 };
8
9 void
10 foo(S0& /*parameter_name*/)
11 {
12 // do something with parameter_name.
13 }
$
$ cat -n test-v1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
3
4 struct S0
5 {
6 char inserted_member;
7 int m0;
8 };
9
10 void
11 bar(S0& /*parameter_name*/)
12 {
13 // do something with parameter_name.
14 }
$
$ g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
$ g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
$
$ ../build/tools/abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 1 Removed, 0 Changed, 1 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 Removed function:
'function void foo(S0&)' {_Z3fooR2S0}
1 Added function:
'function void bar(S0&)' {_Z3barR2S0}
$
4. Comparing two sets of binaries that are passed on the
command line:
$ abidiff --add-binaries1=file2-v1 \
--add-binaries2=file2-v2,file2-v1 \
--added-binaries-dir1 dir1 \
--added-binaries-dir2 dir2 \
file1-v1 file1-v2
Note that the files file2-v1, and file2-v2 are to be found
in dir1 and dir2 or in the current directory.
5. Compare two libraries and their dependencies:
$ abidiff --follow-dependencies \
--added-binaries-dir1 /some/where \
--added-binaries-dir2 /some/where/else \
foo bar
This compares the set of binaries comprised by foo and its
dependencies against the set of binaries comprised by bar
and its dependencies.
abipkgdiff
abipkgdiff compares the Application Binary Interfaces (ABI) of
the ELF binaries contained in two software packages. The
software package formats currently supported are Deb, RPM, tar
archives (either compressed or not) and plain directories that
contain binaries.
For a comprehensive ABI change report that includes changes about
function and variable sub-types, the two input packages must be
accompanied with their debug information packages that contain
debug information either in DWARF, CTF or in BTF formats. Please
note however that some packages contain binaries that embed the
debug information directly in a section of said binaries. In
those cases, obviously, no separate debug information package is
needed as the tool will find the debug information inside the
binaries.
By default, abipkgdiff uses debug information in DWARF format, if
present, otherwise it compares binaries interfaces using debug
information in CTF or in BTF formats, if present. Finally, if no
debug info in these formats is found, it only considers ELF
symbols and report about their addition or removal.
This tool uses the libabigail library to analyze the binary as
well as its associated debug information. Here is its general
mode of operation.
When instructed to do so, a binary and its associated debug
information is read and analyzed. To that effect, libabigail
analyzes by default the descriptions of the types reachable by
the interfaces (functions and variables) that are visible outside
of their translation unit. Once that analysis is done, an
Application Binary Interface Corpus is constructed by only
considering the subset of types reachable from interfaces
associated to ELF symbols that are defined and exported by the
binary. It's that final ABI corpus which libabigail considers as
representing the ABI of the analyzed binary.
Libabigail then has capabilities to generate textual
representations of ABI Corpora, compare them, analyze their
changes and report about them.
Invocation
abipkgdiff [option] <package1> <package2>
package1 and package2 are the packages that contain the binaries
to be compared.
Environment
abipkgdiff loads two default suppression specifications files,
merges their content and use it to filter out ABI change reports
that might be considered as false positives to users.
• Default system-wide suppression specification file
It's located by the optional environment variable
LIBABIGAIL_DEFAULT_SYSTEM_SUPPRESSION_FILE. If that
environment variable is not set, then abipkgdiff tries to load
the suppression file
$libdir/libabigail/libabigail-default.abignore. If that file
is not present, then no default system-wide suppression
specification file is loaded.
• Default user suppression specification file.
It's located by the optional environment
LIBABIGAIL_DEFAULT_USER_SUPPRESSION_FILE. If that environment
variable is not set, then abipkgdiff tries to load the
suppression file $HOME/.abignore. If that file is not present,
then no default user suppression specification is loaded.
In addition to those default suppression specification files,
abipkgdiff will also look inside the packages being compared and
if it sees a file that ends with the extension .abignore, then it
will consider it as a suppression specification and it will
combine it to the default suppression specification that might be
already loaded.
The user might as well use the --suppressions option (that is
documented further below) to provide a suppression specification.
Options
• --help | -h
Display a short help about the command and exit.
• --version | -v
Display the version of the program and exit.
• --debug-info-pkg1 | --d1 <path>
For cases where the debug information for package1 is split
out into a separate file, tells abipkgdiff where to find
that separate debug information package.
Note that the debug info for package1 can have been split
into several different debug info packages. In that case,
several instances of this options can be provided, along
with those several different debug info packages.
• --debug-info-pkg2 | --d2 <path>
For cases where the debug information for package2 is split
out into a separate file, tells abipkgdiff where to find
that separate debug information package.
Note that the debug info for package2 can have been split
into several different debug info packages. In that case,
several instances of this options can be provided, along
with those several different debug info packages.
• --devel-pkg1 | --devel1 <path>
Specifies where to find the Development Package associated
with the first package to be compared. That Development
Package at path should at least contain header files in
which public types exposed by the libraries (of the first
package to be compared) are defined. When this option is
provided, the tool filters out reports about ABI changes to
types that are NOT defined in these header files.
• --devel-pkg2 | --devel2 <path>
Specifies where to find the Development Package associated
with the second package to be compared. That Development
Package at path should at least contains header files in
which public types exposed by the libraries (of the second
package to be compared) are defined. When this option is
provided, the tool filters out reports about ABI changes to
types that are NOT defined in these header files.
• --drop-private-types
This option is to be used with the --devel-pkg1 and
--devel-pkg2 options. With this option, types that are NOT
defined in the headers are entirely dropped from the
internal representation build by Libabigail to represent the
ABI. They thus don't have to be filtered out from the final
ABI change report because they are not even present in
Libabigail's representation.
Without this option however, those private types are kept in
the internal representation and later filtered out from the
report.
This options thus potentially makes Libabigail consume less
memory. It's meant to be mainly used to optimize the memory
consumption of the tool on binaries with a lot of publicly
defined and exported types.
• --dso-only
Compare ELF files that are shared libraries, only. Do not
compare executable files, for instance.
• --private-dso
By default, abipkgdiff does not compare DSOs that are
private to the RPM package. A private DSO is a DSO which
SONAME is NOT advertised in the "provides" property of the
RPM.
This option instructs abipkgdiff to also compare DSOs that
are NOT advertised in the "provides" property of the RPM.
Please note that the fact that (by default) abipkgdiff skips
private DSO is a feature that is available only for RPMs, at
the moment. We would happily accept patches adding that
feature for other package formats.
• --leaf-changes-only|-l only show leaf changes, so don't show
impact analysis report. This option implies --redundant
The typical output of abipkgdiff and abidiff when comparing
two binaries, that we shall call full impact report, looks
like this
$ abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void fn(C&)' at test-v1.cc:13:1 has some indirect sub-type changes:
parameter 1 of type 'C&' has sub-type changes:
in referenced type 'struct C' at test-v1.cc:7:1:
type size hasn't changed
1 data member change:
type of 'leaf* C::m0' changed:
in pointed to type 'struct leaf' at test-v1.cc:1:1:
type size changed from 32 to 64 bits
1 data member insertion:
'char leaf::m1', at offset 32 (in bits) at test-v1.cc:4:1
$
So in that example the report emits information about how
the data member insertion change of "struct leaf" is
reachable from function "void fn(C&)". In other words, the
report not only shows the data member change on "struct
leaf", but it also shows the impact of that change on the
function "void fn(C&)".
In abidiff (and abipkgdiff) parlance, the change on "struct
leaf" is called a leaf change. So the --leaf-changes-only
--impacted-interfaces options show, well, only the leaf
change. And it goes like this:
$ abidiff -l libtest-v0.so libtest-v1.so
'struct leaf' changed:
type size changed from 32 to 64 bits
1 data member insertion:
'char leaf::m1', at offset 32 (in bits) at test-v1.cc:4:1
one impacted interface:
function void fn(C&)
$
Note how the report ends up by showing the list of
interfaces impacted by the leaf change. That's the effect
of the additional --impacted-interfaces option.
Now if you don't want to see that list of impacted
interfaces, then you can just avoid using the
--impacted-interface option. You can learn about that
option below, in any case.
Please note that when comparing two Linux Kernel packages,
it's this leaf changes report that is emitted, by default.
The normal so-called full impact report can be emitted with
the option --full-impact which is documented later below.
• --impacted-interfaces
When showing leaf changes, this option instructs abipkgdiff
to show the list of impacted interfaces. This option is
thus to be used in addition to the --leaf-changes-only
option, or, when comparing two Linux Kernel packages.
Otherwise, it's simply ignored.
• --full-impact|-f
When comparing two Linux Kernel packages, this function
instructs abipkgdiff to emit the so-called full impact
report, which is the default report kind emitted by the
abidiff tool:
$ abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void fn(C&)' at test-v1.cc:13:1 has some indirect sub-type changes:
parameter 1 of type 'C&' has sub-type changes:
in referenced type 'struct C' at test-v1.cc:7:1:
type size hasn't changed
1 data member change:
type of 'leaf* C::m0' changed:
in pointed to type 'struct leaf' at test-v1.cc:1:1:
type size changed from 32 to 64 bits
1 data member insertion:
'char leaf::m1', at offset 32 (in bits) at test-v1.cc:4:1
$
• --non-reachable-types|-t
Analyze and emit change reports for all the types of the
binary, including those that are not reachable from global
functions and variables.
This option might incur some serious performance degradation
as the number of types analyzed can be huge. However, if
paired with the --devel-pkg{1,2} options, the additional
non-reachable types analyzed are restricted to those defined
in the public headers files carried by the referenced
development packages, thus hopefully making the performance
hit acceptable.
Also, using this option alongside suppression specifications
(by also using the --suppressions option) might help keep
the number of analyzed types (and the potential performance
degradation) in control.
Note that without this option, only types that are reachable
from global functions and variables are analyzed, so the
tool detects and reports changes on these reachable types
only.
• --exported-interfaces-only
By default, when looking at the debug information
accompanying a binary, this tool analyzes the descriptions
of the types reachable by the interfaces (functions and
variables) that are visible outside of their translation
unit. Once that analysis is done, an ABI corpus is
constructed by only considering the subset of types
reachable from interfaces associated to ELF symbols that are
defined and exported by the binary. It's those final ABI
Corpora that are compared by this tool.
The problem with that approach however is that analyzing all
the interfaces that are visible from outside their
translation unit can amount to a lot of data, especially
when those binaries are applications, as opposed to shared
libraries. One example of such applications is the Linux
Kernel. Analyzing massive ABI corpora like these can be
extremely slow.
To mitigate that performance issue, this option allows
libabigail to only analyze types that are reachable from
interfaces associated with defined and exported ELF symbols.
Note that this option is turned on by default when analyzing
the Linux Kernel. Otherwise, it's turned off by default.
• --allow-non-exported-interfaces
When looking at the debug information accompanying a binary,
this tool analyzes the descriptions of the types reachable
by the interfaces (functions and variables) that are visible
outside of their translation unit. Once that analysis is
done, an ABI corpus is constructed by only considering the
subset of types reachable from interfaces associated to ELF
symbols that are defined and exported by the binary. It's
those final ABI Corpora that are compared by this tool.
The problem with that approach however is that analyzing all
the interfaces that are visible from outside their
translation unit can amount to a lot of data, especially
when those binaries are applications, as opposed to shared
libraries. One example of such applications is the Linux
Kernel. Analyzing massive ABI Corpora like these can be
extremely slow.
In the presence of an "average sized" binary however one can
afford having libabigail analyze all interfaces that are
visible outside of their translation unit, using this
option.
Note that this option is turned on by default, unless we are
in the presence of the Linux Kernel.
• --redundant
In the diff reports, do display redundant changes. A
redundant change is a change that has been displayed
elsewhere in a given report.
• --harmless
In the diff report, display only the harmless changes. By
default, the harmless changes are filtered out of the diff
report keep the clutter to a minimum and have a greater
chance to spot real ABI issues.
• --no-linkage-name
In the resulting report, do not display the linkage names of
the added, removed, or changed functions or variables.
• --no-added-syms
Do not show the list of functions, variables, or any symbol
that was added.
• --no-added-binaries
Do not show the list of binaries that got added to the
second package.
Please note that the presence of such added binaries is not
considered like an ABI change by this tool; as such, it
doesn't have any impact on the exit code of the tool. It
does only have an informational value. Removed binaries
are, however, considered as an ABI change.
• --no-abignore
Do not search the package for the presence of suppression
files.
• --no-parallel
By default, abipkgdiff will use all the processors it has
available to execute concurrently. This option tells it not
to extract packages or run comparisons in parallel.
• --no-default-suppression
Do not load the default suppression specification files.
• --suppressions | --suppr <path-to-suppressions>
Use a suppression specification file located at
path-to-suppressions. Note that this option can appear
multiple times on the command line. In that case, all of
the suppression specification files are taken into account.
Please note that, by default, if this option is not
provided, then the default suppression specification files
are loaded .
• --linux-kernel-abi-whitelist | -w <path-to-whitelist>
When comparing two Linux kernel RPM packages, this option
points to the white list of names of ELF symbols of
functions and variables that must be compared for ABI
changes. That white list is called a "Linux kernel ABI
white list".
Any other function or variable which ELF symbol are not
present in that white list will not be considered by the ABI
comparison process.
If this option is not provided -- thus if no white list is
provided -- then the ABI of all publicly defined and
exported functions and global variables by the Linux Kernel
binaries are compared.
Please note that if a white list package is given in
parameter, this option handles it just fine, like if the
--wp option was used.
• --wp <path-to-whitelist-package>
When comparing two Linux kernel RPM packages, this option
points an RPM package containining several white lists of
names of ELF symbols of functions and variables that must be
compared for ABI changes. Those white lists are called
"Linux kernel ABI white lists".
From the content of that white list package, this program
then chooses the appropriate Linux kernel ABI white list to
consider when comparing the ABI of Linux kernel binaries
contained in the Linux kernel packages provided on the
command line.
That choosen Linux kernel ABI white list contains the list
of names of ELF symbols of functions and variables that must
be compared for ABI changes.
Any other function or variable which ELF symbol are not
present in that white list will not be considered by the ABI
comparison process.
Note that this option can be provided twice (not mor than
twice), specifying one white list package for each Linux
Kernel package that is provided on the command line.
If this option is not provided -- thus if no white list is
provided -- then the ABI of all publicly defined and
exported functions and global variables by the Linux Kernel
binaries are compared.
• --no-unreferenced-symbols
In the resulting report, do not display change information
about function and variable symbols that are not referenced
by any debug information. Note that for these symbols not
referenced by any debug information, the change information
displayed is either added or removed symbols.
• --no-show-locs
Do not show information about where in the second shared
library the respective type was changed.
• --show-bytes
Show sizes and offsets in bytes, not bits. By default,
sizes and offsets are shown in bits.
• --show-bits
Show sizes and offsets in bits, not bytes. This option is
activated by default.
• --show-hex
Show sizes and offsets in hexadecimal base.
• --show-dec
Show sizes and offsets in decimal base. This option is
activated by default.
• --no-show-relative-offset-changes
Without this option, when the offset of a data member
changes, the change report not only mentions the older and
newer offset, but it also mentions by how many bits the data
member changes. With this option, the latter is not shown.
• --show-identical-binaries
Show the names of the all binaries compared, including the
binaries whose ABI compare equal. By default, when this
option is not provided, only binaries with ABI changes are
mentionned in the output.
• --fail-no-dbg
Make the program fail and return a non-zero exit code if
couldn't read any of the debug information that comes from
the debug info packages that were given on the command line.
If no debug info package were provided on the command line
then this option is not active.
Note that the non-zero exit code returned by the program as
a result of this option is the constant ABIDIFF_ERROR. To
know the numerical value of that constant, please refer to
the exit code documentation.
• --keep-tmp-files
Do not erase the temporary directory files that are created
during the execution of the tool.
• --verbose
Emit verbose progress messages.
• --self-check
This is used to test the underlying Libabigail library.
When in used, the command expects only on input package,
along with its associated debug info packages. The command
then compares each binary inside the package against its own
ABIXML representation. The result of the comparison should
yield the empty set if Libabigail behaves correctly.
Otherwise, it means there is an issue that ought to be
fixed. This option is used by people interested in
Libabigail development for regression testing purposes.
Here is an example of the use of this option:
$ abipkgdiff --self-check --d1 mesa-libGLU-debuginfo-9.0.1-3.fc33.x86_64.rpm mesa-libGLU-9.0.1-3.fc33.x86_64.rpm
==== SELF CHECK SUCCEEDED for 'libGLU.so.1.3.1' ====
$
• --no-assume-odr-for-cplusplus
When analysing a binary originating from C++ code using
DWARF debug information, libabigail assumes the One
Definition Rule to speed-up the analysis. In that case,
when several types have the same name in the binary, they
are assumed to all be equal.
This option disables that assumption and instructs
libabigail to actually actually compare the types to
determine if they are equal.
• --no-leverage-dwarf-factorization
When analysing a binary which DWARF debug information was
processed with the DWZ tool, the type information is
supposed to be already factorized. That context is used by
libabigail to perform some speed optimizations.
This option disables those optimizations.
• --ctf
This is used to compare packages with CTF debug
information, if present.
• --btf
This is used to compare packages with BTF debug
information, if present.
Return value
The exit code of the abipkgdiff command is either 0 if the ABI of
the binaries compared are equal, or non-zero if they differ or if
the tool encountered an error.
In the later case, the value of the exit code is the same as for
the abidiff tool.
kmidiff
kmidiff compares the binary Kernel Module Interfaces of two Linux
Kernel trees. The binary KMI is the interface that the Linux
Kernel exposes to its modules. The trees we are interested in
here are the result of the build of the Linux Kernel source tree.
General approach
And example of how to build your kernel if you want to compare it
to another one using kmidiff is:
git clone -b v4.5 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux/v4.5
cd linux/v4.5
make allyesconfig all
Then install the modules into a directory, for instance, the
build/modules sub-directory of the your kernel source tree:
mkdir build/modules
make modules_install INSTALL_MOD_DIR=build/modules
Then construct a list of interfaces exported by the kernel, that
you want to compare:
cat > kmi-whitelist << EOF
[kernel_4.5_kmi_whitelist]
init_task
schedule
dev_queue_xmit
__kmalloc
printk
EOF
Suppose you've done something similar for the v4.6 branch of the
Linux kernel, you now have these two directories: linux/v4.5 and
linux/v4.6. Their modules are present under the directories
linux/v4.5/build/modules and linux/v4.6/build/modules.
To Comparing their KMI kmidiff needs to know where to find the
vmlinux binaries and their associated modules. Here would be
what the command line looks like:
kmidiff \
--kmi-whitelist linux/v4.6/kmi-whitelist \
--vmlinux1 linux/v4.5/vmlinux \
--vmlinux2 linux/v4.6/vmlinux \
linux/v4.5/build/modules \
linux/v4.6/build/modules
This tool uses the libabigail library to analyze the binary as
well as its associated debug information. Here is its general
mode of operation.
When instructed to do so, a binary and its associated debug
information is read and analyzed. To that effect, libabigail
analyzes by default the descriptions of the types reachable by
the interfaces (functions and variables) that are visible outside
of their translation unit. Once that analysis is done, an
Application Binary Interface Corpus is constructed by only
considering the subset of types reachable from interfaces
associated to ELF symbols that are defined and exported by the
binary. It's that final ABI corpus which libabigail considers as
representing the ABI of the analyzed binary.
Libabigail then has capabilities to generate textual
representations of ABI Corpora, compare them, analyze their
changes and report about them.
Invocation
More generally, kmidiff is invoked under the form:
kmidiff [options] <first-modules-dir> <second-modules-dir>
Environment
By default, kmidiff compares all the interfaces (exported
functions and variables) between the Kernel and its modules. In
practice, though, some users might want to compare a subset of
the those interfaces.
By default, kmidiff uses debug information in the DWARF debug
info format, if present, otherwise it compares interfaces using
CTF or BTF debug info formats, if present. Finally, if no debug
info in these formats is found, it only considers ELF symbols and
report about their addition or removal.
Users can then define a "white list" of the interfaces to
compare. Such a white list is a just a file in the "INI" format
that looks like:
[kernel_version_x86_64_whitelist]
function1_name
function2_name
global_variable1_name
....
Note that the name of the section (the name that is between the
two brackets) of that INI file just has to end with the string
"whitelist". So you can define the name you want, for instance
[kernel_46_x86_64_whitelist].
Then each line of that whitelist file is the name of an exported
function or variable. Only those interfaces along with the types
reachable from their signatures are going to be compared by
kmidiff recursively.
Note that by default kmidiff analyzes the types reachable from
the interfaces associated with ELF symbols that are defined and
exported by the Linux Kernel as being the union of the vmlinux
binary and all its compiled modules. It then compares those
interfaces (along with their types).
Options
• --help | -h
Display a short help about the command and exit.
• --version | -v
Display the version of the program and exit.
• --verbose
Display some verbose messages while executing.
• --debug-info-dir1 | --d1 <di-path1>
For cases where the debug information for the binaries of
the first Linux kernel is split out into separate files,
tells kmidiff where to find those separate debug information
files.
Note that di-path must point to the root directory under
which the debug information is arranged in a tree-like
manner. Under Red Hat based systems, that directory is
usually <root>/usr/lib/debug.
• --debug-info-dir2 | --d2 <di-path2>
Like --debug-info-dir1, this options tells kmidiff where to
find the split debug information for the binaries of the
second Linux kernel.
• --vmlinux1 | --l1 <path-to-first-vmlinux>
Sets the path to the first vmlinux binary to consider. This
has to be the uncompressed vmlinux binary compiled with
debug info.
• --vmlinux2 | --l2 <path-to-first-vmlinux>
Sets the path to the second vmlinux binary to consider.
This has to be the uncompressed vmlinux binary compiled with
debug info.
• --kmi-whitelist | -w <path-to-interface-whitelist>
Set the path to the white list of interfaces to compare
while comparing the Kernel Module Interface of the first
kernel against the one of the second kernel.
If this option is not provided, all the exported interfaces
of the two kernels are compared. That takes a lot of times
and is not necessarily meaningful because many interface are
probably meant to see their reachable types change.
So please, make sure you always use this option unless you
really know what you are doing.
• --suppressions | --suppr <path-to-suppressions>
Use a suppression specification file located at
path-to-suppressions. Note that this option can appear
multiple times on the command line. In that case, all of
the provided suppression specification files are taken into
account.
Please note that, by default, if this option is not
provided, then the default suppression specification files
are loaded .
• --no-change-categorization | -x
This option disables the categorization of changes into
harmless and harmful changes. Note that this categorization
is a pre-requisite for the filtering of changes so this
option disables that filtering. The goal of this option is
to speed-up the execution of the program for cases where the
graph of changes is huge and where the user is just
interested in looking at, for instance, leaf node changes
without caring about their possible impact on interfaces.
• --ctf
Extract ABI information from CTF debug information, if
present, in the Kernel and Modules.
• --btf
Extract ABI information from BTF debug information, if
present, in the Kernel and Modules.
• --impacted-interfaces | -i
Tell what interfaces got impacted by each individual ABI
change.
• --full-impact | -f
Emit a change report that shows the full impact of each
change on exported interfaces. This is the default kind of
report emitted by tools like abidiff or abipkgdiff.
• --exported-interfaces-only
When using this option, this tool analyzes the descriptions
of the types reachable by the interfaces (functions and
variables) associated with ELF symbols that are defined and
exported by the Linux Kernel.
Otherwise, the tool also has the ability to analyze the
descriptions of the types reachable by the interfaces
associated with ELF symbols that are visible outside their
translation unit. This later possibility is however much
more resource intensive and results in much slower
operations.
That is why this option is enabled by default.
• --allow-non-exported-interfaces
When using this option, this tool analyzes the descriptions
of the types reachable by the interfaces (functions and
variables) that are visible outside of their translation
unit. Once that analysis is done, an ABI Corpus is
constructed by only considering the subset of types
reachable from interfaces associated to ELF symbols that are
defined and exported by the binary. It's that final ABI
corpus which is compared against another one.
The problem with that approach however is that analyzing all
the interfaces that are visible from outside their
translation unit can amount to a lot of data, leading to
very slow operations.
Note that this option is turned off by default.
• --show-bytes
Show sizes and offsets in bytes, not bits. This option is
activated by default.
• --show-bits
Show sizes and offsets in bits, not bytes. By default,
sizes and offsets are shown in bytes.
• --show-hex
Show sizes and offsets in hexadecimal base. This option is
activated by default.
• --show-dec
Show sizes and offsets in decimal base.
abidw
abidw reads a shared library in ELF format and emits an XML
representation of its ABI to standard output. The emitted
representation format, named ABIXML, includes all the globally
defined functions and variables, along with a complete
representation of their types. It also includes a representation
of the globally defined ELF symbols of the file.
When given the --linux-tree option, this program can also handle
a Linux kernel tree. That is, a directory tree that contains
both the vmlinux binary and Linux Kernel modules. It analyses
those Linux Kernel binaries and emits an XML representation of
the interface between the kernel and its module, to standard
output. In this case, we don't call it an ABI, but a KMI (Kernel
Module Interface). The emitted KMI includes all the globally
defined functions and variables, along with a complete
representation of their types.
To generate either ABI or KMI representation, by default abidw
uses debug information in the DWARF format, if present, otherwise
it looks for debug information in CTF or BTF formats, if present.
Finally, if no debug info in these formats is found, it only
considers ELF symbols and report about their addition or removal.
This tool uses the libabigail library to analyze the binary as
well as its associated debug information. Here is its general
mode of operation.
When instructed to do so, a binary and its associated debug
information is read and analyzed. To that effect, libabigail
analyzes by default the descriptions of the types reachable by
the interfaces (functions and variables) that are visible outside
of their translation unit. Once that analysis is done, an
Application Binary Interface Corpus is constructed by only
considering the subset of types reachable from interfaces
associated to ELF symbols that are defined and exported by the
binary. It's that final ABI corpus which libabigail considers as
representing the ABI of the analyzed binary.
Libabigail then has capabilities to generate textual
representations of ABI Corpora, compare them, analyze their
changes and report about them.
Invocation
abidw [options] [<path-to-elf-file>]
Options
• --help | -h
Display a short help about the command and exit.
• --version | -v
Display the version of the program and exit.
• --abixml-version
Display the version of the ABIXML format emitted by this
program and exit.
• --add-binaries <bin1,bin2,...>
For each of the comma-separated binaries given in argument
to this option, if the binary is found in the directory
specified by the --added-binaries-dir option, then load the
ABI corpus of the binary and add it to a set of ABI corpora
(called a ABI Corpus Group) made of the binary denoted by
the Argument of abidw. That corpus group is then serialized
out.
• --follow-dependencies
For each dependency of the input binary of abidw, if it is
found in the directory specified by the --added-binaries-dir
option, then construct an ABI corpus out of the dependency
and add it to a set of ABI corpora (called an ABI Corpus
Group) along with the ABI corpus of the input binary of the
program. The ABI Corpus Group is then serialized out.
• --list-dependencies
For each dependency of the input binary of``abidw``, if it's
found in the directory specified by the --added-binaries-dir
option, then the name of the dependency is printed out.
• --added-binaries-dir | --abd <dir-path>
This option is to be used in conjunction with the
--add-binaries, the --follow-dependencies or the
--list-dependencies option. Binaries listed as arguments of
the --add-binaries option or being dependencies of the input
binary in the case of the --follow-dependencies option and
found in the directory <dir-path> are going to be loaded as
ABI corpus and added to the set of ABI corpora (called an
ABI corpus group) built and serialized.
• --debug-info-dir | -d <dir-path>
In cases where the debug info for path-to-elf-file is in a
separate file that is located in a non-standard place, this
tells abidw where to look for that debug info file.
Note that dir-path must point to the root directory under
which the debug information is arranged in a tree-like
manner. Under Red Hat based systems, that directory is
usually <root>/usr/lib/debug.
This option can be provided several times with different
root directories. In that case, abidw will potentially look
into all those root directories to find the split debug info
for the elf file.
Note that this option is not mandatory for split debug
information installed by your system's package manager
because then abidw knows where to find it.
• --out-file | -o <file-path>
This option instructs abidw to emit the XML representation
of path-to-elf-file into the file file-path, rather than
emitting it to its standard output.
• --noout
This option instructs abidw to not emit the XML
representation of the ABI. So it only reads the ELF and
debug information, builds the internal representation of the
ABI and exits. This option is usually useful for debugging
purposes.
• --no-corpus-path
Do not emit the path attribute for the ABI corpus.
• --suppressions | suppr
<path-to-suppression-specifications-file>
Use a suppression specification file located at
path-to-suppression-specifications-file. Note that this
option can appear multiple times on the command line. In
that case, all of the provided suppression specification
files are taken into account. ABI artifacts matched by the
suppression specifications are suppressed from the output of
this tool.
• --kmi-whitelist | -kaw <path-to-whitelist>
When analyzing a Linux Kernel binary, this option points to
the white list of names of ELF symbols of functions and
variables which ABI must be written out. That white list is
called a " Kernel Module Interface white list". This is
because for the Kernel, we don't talk about the ABI; we
rather talk about the interface between the Kernel and its
module. Hence the term KMI rather than ABI
Any other function or variable which ELF symbol are not
present in that white list will not be considered by the KMI
writing process.
If this option is not provided -- thus if no white list is
provided -- then the entire KMI, that is, all publicly
defined and exported functions and global variables by the
Linux Kernel binaries is emitted.
• --linux-tree | --lt
Make abidw to consider the input path as a path to a
directory containing the vmlinux binary as several kernel
modules binaries. In that case, this program emits the
representation of the Kernel Module Interface (KMI) on the
standard output.
Below is an example of usage of abidw on a Linux Kernel
tree.
First, checkout a Linux Kernel source tree and build it.
Then install the kernel modules in a directory somewhere.
Copy the vmlinux binary into that directory too. And then
serialize the KMI of that kernel to disk, using abidw:
$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
$ cd linux && git checkout v4.5
$ make allyesconfig all
$ mkdir build-output
$ make INSTALL_MOD_PATH=./build-output modules_install
$ cp vmlinux build-output/modules/4.5.0
$ abidw --linux-tree build-output/modules/4.5.0 > build-output/linux-4.5.0.kmi
• --headers-dir | --hd <headers-directory-path-1>
Specifies where to find the public headers of the binary
that the tool has to consider. The tool will thus filter
out types that are not defined in public headers.
Note that several public header directories can be specified
for the binary to consider. In that case the --header-dir
option should be present several times on the command line,
like in the following example:
$ abidw --header-dir /some/path \
--header-dir /some/other/path \
binary > binary.abi
• --header-file | --hf <header-file-path>
Specifies where to find one of the public headers of the abi
file that the tool has to consider. The tool will thus
filter out types that are not defined in public headers.
• --drop-private-types
This option is to be used with the --headers-dir and/or
header-file options. With this option, types that are NOT
defined in the headers are entirely dropped from the
internal representation build by Libabigail to represent the
ABI and will not end up in the abi XML file.
• --no-elf-needed
Do not include the list of DT_NEEDED dependency names in the
corpus.
• --drop-undefined-syms
With this option functions or variables for which the
(exported) ELF symbol is undefined are dropped from the
internal representation build by Libabigail to represent the
ABI and will not end up in the abi XML file.
• --exported-interfaces-only
By default, when looking at the debug information
accompanying a binary, this tool analyzes the descriptions
of the types reachable by the interfaces (functions and
variables) that are visible outside of their translation
unit. Once that analysis is done, an ABI corpus is
constructed by only considering the subset of types
reachable from interfaces associated to ELF symbols that are
defined and exported by the binary. It's that final ABI
corpus which textual representation is saved as ABIXML.
The problem with that approach however is that analyzing all
the interfaces that are visible from outside their
translation unit can amount to a lot of data, especially
when those binaries are applications, as opposed to shared
libraries. One example of such applications is the Linux
Kernel. Analyzing massive ABI corpora like these can be
extremely slow.
To mitigate that performance issue, this option allows
libabigail to only analyze types that are reachable from
interfaces associated with defined and exported ELF symbols.
Note that this option is turned on by default when analyzing
the Linux Kernel. Otherwise, it's turned off by default.
• --allow-non-exported-interfaces
When looking at the debug information accompanying a binary,
this tool analyzes the descriptions of the types reachable
by the interfaces (functions and variables) that are visible
outside of their translation unit. Once that analysis is
done, an ABI corpus is constructed by only considering the
subset of types reachable from interfaces associated to ELF
symbols that are defined and exported by the binary. It's
that final ABI corpus which textual representation is saved
as ABIXML.
The problem with that approach however is that analyzing all
the interfaces that are visible from outside their
translation unit can amount to a lot of data, especially
when those binaries are applications, as opposed to shared
libraries. One example of such applications is the Linux
Kernel. Analyzing massive ABI corpora like these can be
extremely slow.
In the presence of an "average sized" binary however one can
afford having libabigail analyze all interfaces that are
visible outside of their translation unit, using this
option.
Note that this option is turned on by default, unless we are
in the presence of the Linux Kernel.
• --no-linux-kernel-mode
Without this option, if abipkgiff detects that the binaries
it is looking at are Linux Kernel binaries (either vmlinux
or modules) then it only considers functions and variables
which ELF symbols are listed in the __ksymtab and
__ksymtab_gpl sections.
With this option, abipkgdiff considers the binary as a
non-special ELF binary. It thus considers functions and
variables which are defined and exported in the ELF sense.
• --check-alternate-debug-info <elf-path>
If the debug info for the file elf-path contains a reference
to an alternate debug info file, abidw checks that it can
find that alternate debug info file. In that case, it emits
a meaningful success message mentioning the full path to the
alternate debug info file found. Otherwise, it emits an
error code.
• --no-show-locs
In the emitted ABI representation, do not show file, line
or column where ABI artifacts are defined.
• --no-parameter-names
In the emitted ABI representation, do not show names of
function parameters, just the types.
• --no-write-default-sizes
In the XML ABI representation, do not write the size-in-bits
for pointer type definitions, reference type definitions,
function declarations and function types when they are equal
to the default address size of the translation unit. Note
that libabigail before 1.8 will not set the default size and
will interpret types without a size-in-bits attribute as
zero sized.
• --type-id-style <sequence``|``hash>
This option controls how types are idenfied in the generated
XML files. The default sequence style just numbers (with
type-id- as prefix) the types in the order they are
encountered. The hash style uses a (stable, portable) hash
of libabigail's internal type names and is intended to make
the XML files easier to diff.
• --check-alternate-debug-info-base-name <elf-path>
Like --check-alternate-debug-info, but in the success
message, only mention the base name of the debug info file;
not its full path.
• --load-all-types
By default, libabigail (and thus abidw) only loads types
that are reachable from functions and variables declarations
that are publicly defined and exported by the binary. So
only those types are present in the output of abidw. This
option however makes abidw load all the types defined in the
binaries, even those that are not reachable from public
declarations.
• --no-load-undefined-interfaces
By default, libabigail (and thus abidw) loads information
about undefined function and variable symbols as well as
functions and variables that are associated with those
undefined symbols. Those are called undefined interfaces.
This option however makes makes abidw avoid loading
information about undefined interfaces. The resulting XML
file thus doesn't contain information about those undefined
interfaces.
• --abidiff
Load the ABI of the ELF binary given in argument, save it
in libabigail's XML format in a temporary file; read the
ABI from the temporary XML file and compare the ABI that
has been read back against the ABI of the ELF binary given
in argument. The ABIs should compare equal. If they
don't, the program emits a diagnostic and exits with a
non-zero code.
This is a debugging and sanity check option.
• --debug-abidiff
Same as --abidiff but in debug mode. In this mode, error
messages are emitted for types which fail type
canonicalization.
This is an optional debugging and sanity check option. To
enable it the libabigail package needs to be configured
with the --enable-debug-self-comparison option.
• --debug-type-canonicalization | --debug-tc
Debug the type canonicalization process. This is done by
using structural and canonical equality when
canonicalizing every single type. Structural and
canonical equality should yield the same result. If they
don't yield the same result for a given type, then it
means that the canonicalization of that type went wrong.
In that case, an error message is emitted and the
execution of the program is aborted.
This option is available only if the package was
configured with the --enable-debug-type-canonicalization
option.
• --no-assume-odr-for-cplusplus
When analysing a binary originating from C++ code using
DWARF debug information, libabigail assumes the One
Definition Rule to speed-up the analysis. In that case,
when several types have the same name in the binary, they
are assumed to all be equal.
This option disables that assumption and instructs
libabigail to actually actually compare the types to
determine if they are equal.
• --no-leverage-dwarf-factorization
When analysing a binary which DWARF debug information was
processed with the DWZ tool, the type information is
supposed to be already factorized. That context is used by
libabigail to perform some speed optimizations.
This option disables those optimizations.
• --ctf
Extract ABI information from CTF debug information, if
present in the given object.
• --annotate
Annotate the ABIXML output with comments above most
elements. The comments are made of the pretty-printed
form types, declaration or even ELF symbols. The purpose
is to make the ABIXML output more human-readable for
debugging or documenting purposes.
• --stats
Emit statistics about various internal things.
• --verbose
Emit verbose logs about the progress of miscellaneous
internal things.
Usage examples
1. Emitting an ABIXML representation of a binary:
$ abidw binary > binary.abi
2. Emitting an ABIXML representation of a set of binaries
specified on the command line:
$ abidw --added-binaries=bin1,bin2,bin3 \
--added-binaries-dir /some/where \
binary > binaries.abi
Note that the binaries bin1, bin2 and bin3 are to be found
in the directory /some/where. A representation of the ABI
of the set of binaries binary, bin1, bin2 and bin3 called
an ABI corpus group is serialized in the file binaries.abi.
3. Emitting an ABIXML representation of a binary and its
dependencies:
$ abidw --follow-dependencies \
--added-binaries-dir /some/where \
binary > binary.abi
Note that only the dependencies that are found in the
directory /some/where are analysed. Their ABIs, along with
the ABI the binary named binary are represented as an ABI
corpus group and serialized in the file binary.abi, in the
ABIXML format.
Notes
Alternate debug info files
As of the version 4 of the DWARF specification, Alternate debug
information is a GNU extension to the DWARF specification. It
has however been proposed for inclusion into the upcoming version
5 of the DWARF standard. You can read more about the GNU
extensions to the DWARF standard here.
abidb
abidb manages a git repository of abixml files describing shared
libraries, and checks binaries against them. elfutils and
libabigail programs are used to query and process the binaries.
abidb works well with debuginfod to fetch needed DWARF content
automatically.
Invocation
abidb [OPTIONS] [--submit PATH1 PATH2 ...] [--check PATH1 PATH2 ...]
Common Options
• --abicompat PATH
Specify the path to the abicompat program to use. By
default, in the absence of this option, the abicompat
program found in directories listed in the $PATH environment
is used.
• --abidw PATH
Specify the path to the abidw program to use. By default,
in the absence of this option, the abidw program found in
directories listed in the $PATH environment is used.
• --distrobranch BRANCH
Specify the git branch for the abixml files in the git repo.
The default is a string like DISTRO/VERSION/ARCHITECTURE,
computed from the running environment.
• --git REPO
Specify the preexisting git working tree for abidb to submit
to or check against. The default is the current working
directory. It may be used concurrently by multiple "check"
operations, but only one "submit" operation.
• --help | -h
Display a short help about the command and exit.
• --loglevel LOGLEVEL
Specify the diagnostic level for messages to stderr. One of
debug, info, warning, error, or critical; case-insensitive.
The default is info.
• --timeout SECONDS
Specify a maximum limit to the execution time (in seconds)
allowed for the abidw and abicompat programs that are
executed. By default, no limit is set for the execution
time of these programs.
Submit Options
• --archive | -Z .EXT[=CMD]
Designate PATH names with a .EXT suffix to be treated as
archives. If CMD is present, pipe the PATH through the
given shell command, otherwise pass as if through cat. The
resulting stream is then opened by libarchive, to enumerate
the contents of a wide variety of possible archive file
format. Process each file in the archive individually into
abixml.
For example, -Z .zip will process each file in a zip file,
and -Z .deb='dpkg-deb --fsys-tarfile' will process each
payload file in a Debian archive.
• --filter REGEX
Limit files selected for abixml extraction to those that
match the given regular expression. The default is
/lib.*\.so, as a heuristic to identify shared libraries.
• --submit PATH1 PATH2 ...
Using abidw, extract abixml for each of the listed files,
generally shared libraries, subject to the filename filter
and the archive decoding options. Save the output of each
abidw run into the selected distrobranch of the selected git
repo. If --submit and --check are both given, do submit
operations first.
• --sysroot PREFIX Specify the a prefix path that is to be
removed from submitted file names.
Check Options
• --check PATH1 PATH2 ...
Using abidiff, compare each of the listed file, generally
executables, against abixml documents for selected versions
for all shared libraries needed by the executable. These
are listed by enumerating the dynamic segment tags DT_NEEDED
of the executable.
• --ld-library-path DIR1:DIR2:DIR3...
Select the search paths for abixml documents used to locate
any particular SONAME . The first given directory wins.
However, all versions of the same SONAME in that directory
are selected for comparison. The default is unspecified,
which means to search for all matching SONAME entries in the
distrobranch, regardless of specific directory.
Exit Code
In case of successful submission and/or checking of all paths,
the exit code is 0.
In case of error, the exit code of abidb is nonzero, and a brief
listing of the binaries unable to be submitted and/or checked is
printed.
Git Repository Schema
abidb stores abixml documents in a git repo with the following
naming schema within the distrobranch:
1. The directory path leading to the shared library file
2. The SONAME of the shared library file, as a subdirectory name
3. A file named BUILDID.xml, where BUILDID is the hexadecimal ELF
build-id note of the shared library.
For example:
┌───────────────────────────┬───────────────────────────────────────────────────────────────────┐
│ shared library file name │ abixml path in git │
├───────────────────────────┼───────────────────────────────────────────────────────────────────┤
│ /usr/lib64/libc.so.6.2.32 │ /usr/lib64/libc.so.6/788cdd41a15985bf8e0a48d213a46e07d58822df.xml │
│ /usr/lib64/libc.so.6.2.33 │ /usr/lib64/libc.so.6/e2ca832f1c2112aea9d7b9bc639e97e873a6b516.xml │
│ /lib/ld-linux.so.2 │ /lib/ld-linux.so.2/b65f3c15b129f33f44f504da1719926aec03c07d.xml │
└───────────────────────────┴───────────────────────────────────────────────────────────────────┘
The intent of including the buildid in the name is so that as a
distro is updated with multiple versions of a given shared
library, they can be represented nearby but non-conflicting. The
SONAME is used in the second-last name component, inspired the
behavior of ld.so and ldconfig, which rely on symbolic links to
map references from the SONAME to an actual file.
See Also
• ELF:
http://en.wikipedia.org/wiki/Executable_and_Linkable_Format
• DWARF: https://www.dwarfstd.org
• Debuginfod: https://sourceware.org/elfutils/Debuginfod.html
• Git: https://git-scm.com/
• Libarchive: https://www.libarchive.org/
abicompat
abicompat checks that an application that links against a given
shared library is still ABI compatible with a subsequent version
of that library. If the new version of the library introduces an
ABI incompatibility, then abicompat hints the user at what
exactly that incompatibility is.
Invocation
abicompat [options] [<application> <shared-library-first-version> <shared-library-second-version>]
Options
• --help
Display a short help about the command and exit.
• --version | -v
Display the version of the program and exit.
• --list-undefined-symbols | -u
Display the list of undefined symbols of the application and
exit.
• --show-base-names | -b
In the resulting report emitted by the tool, this option
makes the application and libraries be referred to by their
base names only; not by a full absolute name. This can be
useful for use in scripts that wants to compare names of the
application and libraries independently of what their
directory names are.
• --app-debug-info-dir | --appd
<path-to-app-debug-info-directory>
Set the path to the directory under which the debug
information of the application is supposed to be laid out.
This is useful for application binaries for which the debug
info is in a separate set of files.
• --lib-debug-info-dir1 | --libd1 <path-to-lib1-debug-info>
Set the path to the directory under which the debug
information of the first version of the shared library is
supposed to be laid out. This is useful for shared library
binaries for which the debug info is in a separate set of
files.
• --lib-debug-info-dir2 | --libd2 <path-to-lib1-debug-info>
Set the path to the directory under which the debug
information of the second version of the shared library is
supposed to be laid out. This is useful for shared library
binaries for which the debug info is in a separate set of
files.
• --suppressions | --suppr <path-to-suppressions>
Use a suppression specification file located at
path-to-suppressions. Note that this option can appear
multiple times on the command line; all the suppression
specification files are then taken into account.
• --no-show-locs
Do not show information about where in the second shared
library the respective type was changed.
• --btf
When comparing binaries, extract ABI information from BTF
debug information, if present.
• --ctf
When comparing binaries, extract ABI information from CTF
debug information, if present.
• --fail-no-debug-info
If no debug info was found, then this option makes the
program to fail. Otherwise, without this option, the
program will attempt to compare properties of the binaries
that are not related to debug info, like pure ELF
properties.
• --ignore-soname
Ignore differences in the SONAME when doing a comparison
• --weak-mode
This triggers the weak mode of abicompat. In this mode,
only one version of the library is required. That is,
abicompat is invoked like this:
abicompat --weak-mode <the-application> <the-library>
Note that the --weak-mode option can even be omitted if only
one version of the library is given, along with the
application; in that case, abicompat automatically switches
to operate in weak mode:
abicompat <the-application> <the-library>
In this weak mode, the types of functions and variables
exported by the library and consumed by the application (as
in, the symbols of the these functions and variables are
undefined in the application and are defined and exported by
the library) are compared to the version of these types as
expected by the application. And if these two versions of
types are different, abicompat tells the user what the
differences are.
In other words, in this mode, abicompat checks that the
types of the functions and variables exported by the library
mean the same thing as what the application expects, as far
as the ABI is concerned.
Note that in this mode, abicompat doesn't detect exported
functions or variables (symbols) that are expected by the
application but that are removed from the library. That is
why it is called weak mode.
Return values
The exit code of the abicompat command is either 0 if the ABI of
the binaries being compared are equal, or non-zero if they differ
or if the tool encountered an error.
In the later case, the exit code is a 8-bits-wide bit field in
which each bit has a specific meaning.
The first bit, of value 1, named ABIDIFF_ERROR means there was an
error.
The second bit, of value 2, named ABIDIFF_USAGE_ERROR means there
was an error in the way the user invoked the tool. It might be
set, for instance, if the user invoked the tool with an unknown
command line switch, with a wrong number or argument, etc. If
this bit is set, then the ABIDIFF_ERROR bit must be set as well.
The third bit, of value 4, named ABIDIFF_ABI_CHANGE means the ABI
of the binaries being compared are different.
The fourth bit, of value 8, named ABIDIFF_ABI_INCOMPATIBLE_CHANGE
means the ABI of the binaries compared are different in an
incompatible way. If this bit is set, then the
ABIDIFF_ABI_CHANGE bit must be set as well. If the
ABIDIFF_ABI_CHANGE is set and the ABIDIFF_INCOMPATIBLE_CHANGE is
NOT set, then it means that the ABIs being compared might or
might not be compatible. In that case, a human being needs to
review the ABI changes to decide if they are compatible or not.
The remaining bits are not used for the moment.
Usage examples
• Detecting a possible ABI incompatibility in a new shared
library version:
$ cat -n test0.h
1 struct foo
2 {
3 int m0;
4
5 foo()
6 : m0()
7 {}
8 };
9
10 foo*
11 first_func();
12
13 void
14 second_func(foo&);
15
16 void
17 third_func();
$
$ cat -n test-app.cc
1 // Compile with:
2 // g++ -g -Wall -o test-app -L. -ltest-0 test-app.cc
3
4 #include "test0.h"
5
6 int
7 main()
8 {
9 foo* f = first_func();
10 second_func(*f);
11 return 0;
12 }
$
$ cat -n test0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-0.so test0.cc
3
4 #include "test0.h"
5
6 foo*
7 first_func()
8 {
9 foo* f = new foo();
10 return f;
11 }
12
13 void
14 second_func(foo&)
15 {
16 }
17
18 void
19 third_func()
20 {
21 }
$
$ cat -n test1.h
1 struct foo
2 {
3 int m0;
4 char m1; /* <-- a new member got added here! */
5
6 foo()
7 : m0(),
8 m1()
9 {}
10 };
11
12 foo*
13 first_func();
14
15 void
16 second_func(foo&);
17
18 void
19 third_func();
$
$ cat -n test1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-1.so test1.cc
3
4 #include "test1.h"
5
6 foo*
7 first_func()
8 {
9 foo* f = new foo();
10 return f;
11 }
12
13 void
14 second_func(foo&)
15 {
16 }
17
18 /* Let's comment out the definition of third_func()
19 void
20 third_func()
21 {
22 }
23 */
$
• Compile the first and second versions of the libraries:
libtest-0.so and libtest-1.so:
$ g++ -g -Wall -shared -o libtest-0.so test0.cc
$ g++ -g -Wall -shared -o libtest-1.so test1.cc
• Compile the application and link it against the first
version of the library, creating the test-app binary:
$ g++ -g -Wall -o test-app -L. -ltest-0.so test-app.cc
• Now, use abicompat to see if libtest-1.so is ABI
compatible with app, with respect to the ABI of
libtest-0.so:
$ abicompat test-app libtest-0.so libtest-1.so
ELF file 'test-app' might not be ABI compatible with 'libtest-1.so' due to differences with 'libtest-0.so' below:
Functions changes summary: 0 Removed, 2 Changed, 0 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
2 functions with some indirect sub-type change:
[C]'function foo* first_func()' has some indirect sub-type changes:
return type changed:
in pointed to type 'struct foo':
size changed from 32 to 64 bits
1 data member insertion:
'char foo::m1', at offset 32 (in bits)
[C]'function void second_func(foo&)' has some indirect sub-type changes:
parameter 0 of type 'foo&' has sub-type changes:
referenced type 'struct foo' changed, as reported earlier
$
• Now use the weak mode of abicompat, that is, providing
just the application and the new version of the library:
$ abicompat --weak-mode test-app libtest-1.so
functions defined in library
'libtest-1.so'
have sub-types that are different from what application
'test-app'
expects:
function foo* first_func():
return type changed:
in pointed to type 'struct foo':
size changed from 32 to 64 bits
1 data member insertion:
'char foo::m1', at offset 32 (in bits)
$
abilint
abilint parses the native XML representation of an ABI as emitted
by abidw. Once it has parsed the XML representation of the ABI,
abilint builds and in-memory model from it. It then tries to
save it back to an XML form, to standard output. If that
read-write operation succeeds chances are the input XML ABI
representation is meaningful.
Note that the main intent of this tool to help debugging issues
in the underlying Libabigail library.
Note also that abilint can also read an ELF input file, build the
in-memory model for its ABI, and serialize that model back into
XML to standard output. In that case, the ELF input file must be
accompanied with its debug information in the DWARF format.
Invocation
abilint [options] [<abi-file1>]
Options
• --annotate
Annotate the ABIXML output with comments above most
elements. The comments are made of the pretty-printed form
of types, declaration or even ELF symbols. The purpose is
to make the ABIXML output more human-readable for debugging
or documenting purposes.
• --ctf
Extract ABI information from CTF debug information, if
present in the given object.
• --debug-info-dir <path>
When reading an ELF input file which debug information is
split out into a separate file, this options tells abilint
where to find that separate debug information file.
Note that path must point to the root directory under which
the debug information is arranged in a tree-like manner.
Under Red Hat based systems, that directory is usually
<root>/usr/lib/debug.
Note also that this option is not mandatory for split debug
information installed by your system's package manager
because then abidiff knows where to find it.
• --diff
For XML inputs, perform a text diff between the input and
the memory model saved back to disk. This can help to spot
issues in the handling of the XML format by the underlying
Libabigail library.
• --header-file | --hf <header-file-path>
Specifies where to find one of the public headers of the abi
file that the tool has to consider. The tool will thus
filter out types that are not defined in public headers.
• --headers-dir | --hd <headers-directory-path-1>
Specifies where to find the public headers of the first
shared library that the tool has to consider. The tool will
thus filter out types that are not defined in public
headers.
• --help
Display a short help message and exits.
• --noout
Do not display anything on standard output. The return code
of the command is the only way to know if the command
succeeded.
• --suppressions | suppr
<path-to-suppression-specifications-file>
Use a suppression specification file located at
path-to-suppression-specifications-file. Note that this
option can appear multiple times on the command line. In
that case, all of the provided suppression specification
files are taken into account. ABI artifacts matched by the
suppression specifications are suppressed from the output of
this tool.
• --stdin | --
Read the input content from standard input.
• --tu
Expect the input XML to represent a single translation unit.
• --version | -v
Display the version of the program and exit.
fedabipkgdiff
fedabipkgdiff compares the ABI of shared libraries in Fedora
packages. It's a convenient way to do so without having to
manually download packages from the Fedora Build System.
fedabipkgdiff knows how to talk with the Fedora Build System to
find the right packages versions, their associated debug
information and development packages, download them, compare
their ABI locally, and report about the possible ABI changes.
Note that by default, this tool reports ABI changes about types
that are defined in public header files found in the development
packages associated with the packages being compared. It also
reports ABI changes about functions and global variables whose
symbols are defined and exported in the ELF binaries found in the
packages being compared.
Invocation
fedabipkgdiff [option] <NVR> ...
Environment
fedabipkgdiff loads two default suppression specifications files,
merges their content and use it to filter out ABI change reports
that might be considered as false positives to users.
• Default system-wide suppression specification file
It's located by the optional environment variable
LIBABIGAIL_DEFAULT_SYSTEM_SUPPRESSION_FILE. If that
environment variable is not set, then fedabipkgdiff tries to
load the suppression file
$libdir/libabigail/libabigail-default.abignore. If that file
is not present, then no default system-wide suppression
specification file is loaded.
• Default user suppression specification file.
It's located by the optional environment
LIBABIGAIL_DEFAULT_USER_SUPPRESSION_FILE. If that environment
variable is not set, then fedabipkgdiff tries to load the
suppression file $HOME/.abignore. If that file is not present,
then no default user suppression specification is loaded.
Options
• --help | -h
Display a short help about the command and exit.
• --dry-run
Don't actually perform the ABI comparison. Details about
what is going to be done are emitted on standard output.
• --debug
Emit debugging messages about the execution of the program.
Details about each method invocation, including input
parameters and returned values, are emitted.
• --traceback
Show traceback when an exception raised. This is useful for
developers of the tool itself to know more exceptional
errors.
• --server <URL>
Specifies the URL of the Koji XMLRPC service the tool talks
to. The default value of this option is
http://koji.fedoraproject.org/kojihub .
• --topurl <URL>
Specifies the URL of the package store the tool downloads
RPMs from. The default value of this option is
https://kojipkgs.fedoraproject.org .
• --from <distro>
Specifies the name of the baseline Fedora distribution in
which to find the first build that is used for comparison.
The distro value can be any valid value of the RPM macro
%{?dist} for Fedora, for example, fc4, fc23, fc25.
• --to <distro>
Specifies the name of the Fedora distribution in which to
find the build that is compared against the baseline
specified by option --from. The distro value could be any
valid value of the RPM macro %{?dist} for Fedora, for
example, fc4, fc23.
• --all-subpackages
Instructs the tool to also compare the ABI of the binaries
in the sub-packages of the packages specified.
• --dso-only
Compares the ABI of shared libraries only. If this option
is not provided, the tool compares the ABI of all ELF
binaries found in the packages.
• --suppressions <path-to-suppresions>
Use a suppression specification file located at
path-to-suppressions.
• --no-default-suppression
Do not load the default suppression specification files.
• --no-devel-pkg
Do not take associated development packages into account
when performing the ABI comparison. This makes the tool
report ABI changes about all types that are reachable from
functions and global variables which symbols are defined and
publicly exported in the binaries being compared, even if
those types are not defined in public header files available
from the packages being compared.
• --show-identical-binaries
Show the names of the all binaries compared, including the
binaries whose ABI compare equal. By default, when this
option is not provided, only binaries with ABI changes are
mentionned in the output.
• --abipkgdiff <path/to/abipkgdiff>
Specify an alternative abipkgdiff instead of the one
installed in system.
• --clean-cache-before
Clean cache before ABI comparison.
• --clean-cache-after
Clean cache after ABI comparison.
• --clean-cache
If you want to clean cache both before and after ABI
comparison, --clean-cache is the convenient way for you to
save typing of two options at same time.
Note that a build is a specific version and release of an RPM
package. It's specified by its the package name, version and
release. These are specified by the Fedora Naming Guidelines
Return value
The exit code of the abipkgdiff command is either 0 if the ABI of
the binaries compared are equivalent, or non-zero if they differ
or if the tool encountered an error.
In the later case, the value of the exit code is the same as for
the abidiff tool.
Use cases
Below are some usage examples currently supported by
fedabipkgdiff.
1. Compare the ABI of binaries in a local package against the
ABI of the latest stable package in Fedora 23.
Suppose you have built just built the httpd package and you
want to compare the ABI of the binaries in this locally
built package against the ABI of the binaries in the latest
http build from Fedora 23. The command line invocation
would be:
$ fedabipkgdiff --from fc23 ./httpd-2.4.18-2.fc24.x86_64.rpm
2. Compare the ABI of binaries in two local packages.
Suppose you have built two versions of package httpd, and
you want to see what ABI differences between these two
versions of RPM files. The command line invocation would
be:
$ fedabipkgdiff path/to/httpd-2.4.23-3.fc23.x86_64.rpm another/path/to/httpd-2.4.23-4.fc24.x86_64.rpm
All what fedabipkgdiff does happens on local machine
without the need of querying or downloading RPMs from Koji.
3. Compare the ABI of binaries in the latest build of the
httpd package in Fedora 23 against the ABI of the binaries
in the latest build of the same package in 24.
In this case, note that neither of the two packages are
available locally. The tool is going to talk with the
Fedora Build System, determine what the versions and
releases of the latest packages are, download them and
perform the comparison locally. The command line
invocation would be:
$ fedabipkgdiff --from fc23 --to fc24 httpd
4. Compare the ABI of binaries of two builds of the httpd
package, designated their versions and releases.
If we want to do perform the ABI comparison for all the
processor architectures supported by Fedora the command
line invocation would be:
$ fedabipkgdiff httpd-2.8.14.fc23 httpd-2.8.14.fc24
But if we want to perform the ABI comparison for a specific
architecture, say, x86_64, then the command line invocation
would be:
$ fedabipkgdiff httpd-2.8.14.fc23.x86_64 httpd-2.8.14.fc24.x86_64
5. If the use wants to also compare the sub-packages of a
given package, she can use the --all-subpackages option.
The first command of the previous example would thus look
like:
$ fedabipkgdiff --all-subpackages httpd-2.8.14.fc23 httpd-2.8.14.fc24
ABI artifacts
An ABI artifact is a relevant part of the ABI of a shared library
or program. Examples of ABI artifacts are exported types,
variables, functions, or ELF symbols exported by a shared
library.
The set of ABI artifact for a binary is called an ABI Corpus.
Harmful changes
A change in the diff report is considered harmful if it might
cause ABI compatibility issues. That is, it might prevent an
application dynamically linked against a given version of a
library to keep working with the changed subsequent versions of
the same library.
Harmless changes
A change in the diff report is considered harmless if it will not
cause any ABI compatibility issue. That is, it will not prevent
an application dynamically linked against given version of a
library to keep working with the changed subsequent versions of
the same library.
By default, abidiff filters harmless changes from the diff
report.
Suppression specifications
Definition
A suppression specification file is a way for a user to instruct
abidiff, abipkgdiff or any other relevant libabigail tool to
avoid emitting reports for changes involving certain ABI
artifacts.
It contains directives (or specifications) that describe the set
of ABI artifacts to avoid emitting change reports about.
Introductory examples
Its syntax is based on a simplified and customized form of Ini
File Syntax. For instance, to specify that change reports on a
type named FooPrivateType should be suppressed, one could write
this suppression specification:
[suppress_type]
name = FooPrivateType
If we want to ensure that only change reports about structures
named FooPrivateType should be suppressed, we could write:
[suppress_type]
type_kind = struct
name = FooPrivateType
But we could also want to suppress change reports avoid typedefs
named FooPrivateType. In that case we would write:
[suppress_type]
type_kind = typedef
name = FooPrivateType
Or, we could want to suppress change reports about all struct
which names end with the string "PrivateType":
[suppress_type]
type_kind = struct
name_regexp = ^.*PrivateType
Let's now look at the generic syntax of suppression specification
files.
Syntax
Properties
More generally, the format of suppression lists is organized
around the concept of property. Every property has a name and a
value, delimited by the = sign. E.g:
name = value
Leading and trailing white spaces are ignored around property
names and values.
Regular expressions
The value of some properties might be a regular expression. In
that case, they must comply with the syntax of extended POSIX
regular expressions. Note that Libabigail uses the regular
expression engine of the GNU C Library.
Escaping a character in a regular expression
When trying to match a string that contains a * character, like
in the pointer type int*, one must be careful to notice that the
character * is a special character in the extended POSIX regular
expression syntax. And that character must be escaped for the
regular expression engine. Thus the regular expression that
would match the string int* in a suppression file should be
int\\*
Wait; but then why the two \ characters? Well, because the \
character is a special character in the Ini File Syntax used for
specifying suppressions. So it must be escaped as well, so that
the Ini File parser leaves a \ character intact in the data
stream that is handed to the regular expression engine. Hence
the \\ targeted at the Ini File parser.
So, in short, to escape a character in a regular expression,
always prefix the character with the \\ sequence.
Modus operandi
Suppression specifications can be applied at two different points
of the processing pipeline of libabigail.
In the default operating mode called "late suppression mode",
suppression specifications are applied to the result of comparing
the in-memory internal representations of two ABIs. In this
mode, if an ABI artifact matches a suppression specification, its
changes are not mentioned in the ABI change report. The internal
representation of the "suppressed" changed ABI artifact is still
present in memory; it is just not mentioned in the ABI change
report. The change report can still mention statistics about the
number of changed ABI artifacts that were suppressed.
There is another operating mode called the "early suppression
mode" where suppression specifications are applied during the
construction of the in-memory internal representation of a given
ABI. In that mode, if an ABI artifact matches a suppression
specification, no in-memory internal representation is built for
it. As a result, no change about the matched ABI artifact is
going to be mentioned in the ABI change report and no statistic
about the number of suppressed ABI changes is available. Also,
please note that because suppressed ABI artifacts are removed
from the in-memory internal representation in this mode, the
amount memory used by the internal representation is potentially
smaller than the memory consumption in the late suppression mode.
Sections
Properties are then grouped into arbitrarily named sections that
shall not be nested. The name of the section is on a line by
itself and is surrounded by square brackets, i.e:
[section_name]
property1_name = property1_value
property2_name = property2_value
A section might or might not have properties. Sections that
expect to have properties and which are found nonetheless empty
are just ignored. Properties that are not recognized by the
reader are ignored as well.
Section names
Each different section can be thought of as being a directive to
suppress ABI change reports for a particular kind of ABI
artifact.
[suppress_file]
This directive prevents a given tool from loading a file (binary
or abixml file) if its file name or other properties match
certain properties. Thus, if the tool is meant to compare the
ABIs of two files, and if the directive prevents it from loading
either one of the files, then no comparison is performed.
Note that for the [suppress_file] directive to work, at least one
of the following properties must be provided:
file_name_regexp, file_name_not_regexp, soname_regexp,
soname_not_regexp.
If none of the above properties are provided, then the
[suppress_file] directive is simply ignored.
The potential properties of this sections are listed below:
• file_name_not_regexp
Usage:
file_name_not_regexp = <regular-expression>
Prevents the system from loading the file which name does not
match the regular expression specified as value of this
property.
• file_name_regexp
Usage:
file_name_regexp = <regular-expression>
Prevents the system from loading the file which name matches
the regular expression specified as value of this property.
• label
Usage:
label = <some-value>
Define a label for the section. A label is just an
informative string that might be used by the tool to refer to
a type suppression in error messages. There can also be some
special label names that make the suppression system behave a
certain way.
• soname_regexp
Usage:
soname_regexp = <regular-expression>
Prevents the system from loading the file which contains a
SONAME property that matches the regular expression of this
property. Note that this property also works on an abixml file
if it contains a SONAME property.
• soname_not_regexp
Usage:
soname_not_regexp = <regular-expression>
Prevents the system from loading the file which contains a
SONAME property that does NOT match the regular expression of
this property. Note that this property also works on an abixml
file if it contains a SONAME property.
[suppress_type]
This directive suppresses report messages about a type change.
Note that for the [suppress_type] directive to work, at least one
of the following properties must be provided:
file_name_regexp, file_name_not_regexp, soname_regexp,
soname_not_regexp, name, name_regexp, name_not_regexp,
source_location_not_in, source_location_not_regexp, type_kind.
If none of the above properties are provided, then the
[suppress_type] directive is simply ignored.
The potential properties of this sections are listed below:
• accessed_through
Usage:
accessed_through = <some-predefined-values>
Suppress change reports involving a type which is referred to
either directly or through a pointer or a reference. The
potential values of this property are the predefined keywords
below:
• direct
So if the [suppress_type] contains the property
description:
accessed_through = direct
then changes about a type that is referred-to directly
(i.e, not through a pointer or a reference) are going to
be suppressed.
• pointer
If the accessed_through property is set to the value
pointer then changes about a type that is referred-to
through a pointer are going to be suppressed.
• reference
If the accessed_through property is set to the value
reference then changes about a type that is referred-to
through a reference are going to be suppressed.
• reference-or-pointer
If the accessed_through property is set to the value
reference-or-pointer then changes about a type that is
referred-to through either a reference or a pointer are
going to be suppressed.
For an extensive example of how to use this property, please
check out the example below about suppressing change reports
about types accessed either directly or through pointers.
• changed_enumerators
Usage:
changed_enumerators = <list-of-enumerators>
Suppresses change reports involving changes in the value of
enumerators of a given enum type. This property is applied if
the type_kind property is set to the value enum, at least. The
value of the changed_enumerators is a comma-separated list of
the enumerators that the user expects to change. For instance:
changed_enumerators = LAST_ENUMERATORS0, LAST_ENUMERATOR1
• changed_enumerators_regexp
Usage:
changed_enumerators_regexp =
<list-of-enumerator-regular-expressions>
Suppresses change reports involving changes in the value of
enumerators of a given enum type. This property is applied if
the type_kind property is set to the value enum, at least. The
value of the changed_enumerators_regexp property is a
comma-separated list of regular expressions that should match
the names of the enumerators that the user expects to change.
For instance:
changed_enumerators_regexp = .*_MAX$, .*_LAST$, .*_NUM$, .*_NBITS$
In the example above, change reports to any enumerator which
name ends with _MAX, _LAST, _NUM or _NBITS will be suppressed.
Note that for this property to be applied to changes to an enum
type, the size of the enum type must NOT have changed.
• drop
Usage:
drop = yes | no
If a type is matched by a suppression specification which
contains the "drop" property set to "yes" (or to "true") then
the type is not even going to be represented in the internal
representation of the ABI being analyzed. This property makes
its enclosing suppression specification to be applied in the
early suppression specification mode. The net effect is that
it potentially reduces the amount of memory used to represent
the ABI being analyzed.
Please note that for struct, class or``enum`` types matching a
suppression specification with this property having a value
set to "yes" (or to "true"), if the specification also has a
label property with a value set to
libabigail::OPAQUE_TYPE_LABEL, then the type is transformed
into an opaque type, rather than being just dropped on the
floor. That also reduces the amount of memory used to
represent the ABI being analyzed, but with potentially less
disruption in the resulting ABI representation.
Please note that for this property to be effective, the
enclosing suppression specification must have at least one of
the following properties specified: name_regexp, name,
name_regexp, source_location_not_in or
source_location_not_regexp.
• file_name_not_regexp
Usage:
file_name_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a binary file which name does not match the regular
expression specified as value of this property.
• file_name_regexp
Usage:
file_name_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a binary file which name matches the regular expression
specified as value of this property.
• has_data_member
Usage:
has_data_member = <list-of-data-member-names>
Suppresses change reports involving a type which contains data
members whose names are provided in the list value of this
property.
A usage examples of this property would be:
has_data_member = {private_data_member0, private_data_member1}
The property above would match any type which contains at least
two data members whose names are private_data_member0 and
private_data_member1.
Another usage examples of this property would be:
has_data_member = another_private_data_member
The property above would match any type which contains a data
member which name is another_private_data_member0.
• has_data_member_regexp
Usage:
has_data_member_regexp = <a-regular-expression>
Suppresses change reports involving a type which contains data
members whose names match the regular expression provided as the
value of this property.
A usage examples of this property would be:
has_data_member_regexp = ^private_data_member
The property above would match any type which contains data
members whose names match the regular expression
^private_data_member. In other words, it would match any type
which contains data members whose names start with the string
"private_data_member".
• has_data_member_inserted_at
Usage:
has_data_member_inserted_at = <offset-in-bit>
Suppresses change reports involving a type which has at least
one data member inserted at an offset specified by the
property value offset-in-bit. Please note that if the size of
the type changed, then the type change will NOT be suppressed
by the evaluation of this property, unless the has_size_change
property is present and set to yes.
The value offset-in-bit is either:
• an integer value, expressed in bits, which denotes the
offset of the insertion point of the data member,
starting from the beginning of the relevant structure or
class.
• data member offset selector expressions, such as:
• the keyword end which is a named constant which
value equals the offset of the end of the structure
or class.
• the keyword offset_of_flexible_array_data_member
which is a named constant that evaluates to the
offset of the flexible array data member contained
in the relevant structure.
• the function call expression
offset_of(data-member-name) where data-member-name
is the name of a given data member of the relevant
structure or class. The value of this function
call expression is an integer that represents the
offset of the data member denoted by
data-member-name.
• the function call expression
offset_after(data-member-name) where
data-member-name is the name of a given data member
of the relevant structure or class. The value of
this function call expression is an integer that
represents the offset of the point that comes right
after the region occupied by the data member
denoted by data-member-name.
• the function call expression
offset_of_first_data_member_regexp(data-member-name-regexp)
where data-member-name-regexp is a regular
expression matching a data member. The value of
this function call expression is an integer that
represents the offset of the first data member
which name matches the regular expression argument.
If no data member of a given class type matches the
regular expression, then the class type won't match
the current directive.
• the function call expression
offset_of_last_data_member_regexp(data-member-name-regexp)
where data-member-name-regexp is a regular
expression matching a data member. The value of
this function call expression is an integer that
represents the offset of the last data member which
name matches the regular expression argument. If
no data member of a given class type matches the
regular expression, then the class type won't match
the current directive.
• has_data_member_inserted_between
Usage:
has_data_member_inserted_between = {<range-begin>,
<range-end>}
Suppresses change reports involving a type which has at least
one data member inserted at an offset that is comprised in the
range between range-begin and range-end. Please note that
each of the values range-begin and range-end can be of the
same form as the has_data_member_inserted_at property above.
Please also note that if the size of the type changed, then
the type change will NOT be suppressed by the evaluation of
this property, unless the has_size_change property is present
and set to yes. Note that data member deletions happening in
the range between range-begin and range-end won't prevent the
type change from being suppressed by the evaluation of this
property if the size of the type doesn't change or if the
has_size_change property is present and set to yes.
Usage examples of this properties are:
has_data_member_inserted_between = {8, 64}
or:
has_data_member_inserted_between = {16, end}
or:
has_data_member_inserted_between = {offset_after(member1), end}
• has_data_members_inserted_between
Usage:
has_data_members_inserted_between = {<sequence-of-ranges>}
Suppresses change reports involving a type which has multiple
data member inserted in various offset ranges. A usage
example of this property is, for instance:
has_data_members_inserted_between = {{8, 31}, {72, 95}}
This usage example suppresses change reports involving a type
which has data members inserted in bit offset ranges [8 31]
and [72 95]. The length of the sequence of ranges or this
has_data_members_inserted_between is not bounded; it can be as
long as the system can cope with. The values of the
boundaries of the ranges are of the same kind as for the
has_data_member_inserted_at property above. Please also note
that if the size of the type changed, then the type will NOT
be suppressed by the evaluation of this property, unless the
has_size_change property is present and set to yes. Note that
data member deletions happening in the defined ranges won't
prevent the type change from being suppressed by the
evaluation of this property if the size of the type doesn't
change or if the has_size_change property is present and set
to yes.
Another usage example of this property is thus:
has_data_members_inserted_between =
{
{offset_after(member0), offset_of(member1)},
{72, end}
}
• has_strict_flexible_array_data_member_conversion
Usage:
has_strict_flexible_array_data_member_conversion = yes |
no
Suppresses change reports involving a type which has a "fake"
flexible array member at the end of the struct which is
converted to a real flexible array member. This would be a
member like data[1] being converted to data[].
Please note that if the size of the type changed, then the
type change will NOT be suppressed by the evaluation of this
property, unless the has_size_change property is present and
set to yes.
• has_size_change
Usage:
has_size_change = yes | no
This property is to be used in conjunction with the properties
has_data_member_inserted_between,
has_data_members_inserted_between, and
has_strict_flexible_array_data_member_conversion Those properties
will not match a type change if the size of the type changes,
unless the has_size_changes property is set to yes.
• label
Usage:
label = <some-value>
Define a label for the section. In general, a label is just
an informative string that might be used by a tool to refer to
a type suppression in error messages.
Note however that there are some special label values that can
trigger a special kind of behavior. Below are those special
label values:
• libabigail::OPAQUE_TYPE_LABEL: A struct, class or enum
type that matches a [suppress_type] section with this
label property value is going to be replaced by an
opaque type of the same kind. Note that an opaque type
is essentially a declaration-only type, thus with no
member. Also note that for a [suppress_type] section
with this label to trigger the transformation of a type
into an opaque type, the section must have the drop
property value set to yes|true.
• name
Usage:
name = <a-value>
Suppresses change reports involving types whose name equals
the value of this property.
• name_not_regexp
Usage:
name_not_regexp = <regular-expression>
Suppresses change reports involving types whose name does NOT
match the regular expression specified as value of this
property. Said otherwise, this property specifies which types
to keep, rather than types to suppress from reports.
• name_regexp
Usage:
name_regexp = <regular-expression>
Suppresses change reports involving types whose name matches
the regular expression specified as value of this property.
• soname_not_regexp
Usage:
soname_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a shared library which SONAME property does not match the
regular expression specified as value of this property.
• soname_regexp
Usage:
soname_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a shared library which SONAME property matches the regular
expression specified as value of this property.
• source_location_not_in
Usage:
source_location_not_in = <list-of-file-paths>
Suppresses change reports involving a type which is defined in
a file which path is NOT listed in the value
list-of-file-paths. Note that the value is a comma-separated
list of file paths e.g, this property
source_location_not_in = libabigail/abg-ir.h, libabigail/abg-dwarf-reader.h
suppresses change reports about all the types that are NOT
defined in header files whose path end up with the strings
libabigail/abg-ir.h or libabigail/abg-dwarf-reader.h.
• source_location_not_regexp
Usage:
source_location_not_regexp = <regular-expression>
Suppresses change reports involving a type which is defined in
a file which path does NOT match the regular expression
provided as value of the property. E.g, this property
source_location_not_regexp = libabigail/abg-.*\\.h
suppresses change reports involving all the types that are NOT
defined in header files whose path match the regular
expression provided a value of the property.
• type_kind
Usage:
type_kind = class | struct | union | enum |
array | typedef | builtin
Suppresses change reports involving a certain kind of type.
The kind of type to suppress change reports for is specified
by the possible values listed above:
•
class: suppress change reports for class types. Note
that
even if class types don't exist for C, this value
still triggers the suppression of change reports
for struct types, in C. In C++ however, it
should do what it suggests.
•
struct: suppress change reports for struct types in C or
C++.
Note that the value class above is a super-set of
this one.
• union: suppress change reports for union types.
• enum: suppress change reports for enum types.
• array: suppress change reports for array types.
• typedef: suppress change reports for typedef types.
• builtin: suppress change reports for built-in (or
native) types. Example of built-in types are char, int,
unsigned int, etc.
[suppress_function]
This directive suppresses report messages about changes on a set
of functions.
Note that for the [suppress_function] directive to work, at least
one of the following properties must be provided:
label, file_name_regexp, file_name_not_regexp, soname_regexp,
soname_not_regexp, name, name_regexp, name_not_regexp,
parameter, return_type_name, return_type_regexp, symbol_name,
symbol_name_regexp, symbol_name_not_regexp, symbol_version,
symbol_version_regexp.
If none of the above properties are provided, then the
[suppress_function] directive is simply ignored.
The potential properties of this sections are:
• change_kind
Usage:
change_kind = <predefined-possible-values>
Specifies the kind of changes this suppression specification
should apply to. The possible values of this property as well
as their meaning are listed below:
• function-subtype-change
This suppression specification applies to functions that
which have at least one sub-type that has changed.
• added-function
This suppression specification applies to functions that
have been added to the binary.
• deleted-function
This suppression specification applies to functions that
have been removed from the binary.
• all
This suppression specification applies to functions that
have all of the changes above. Note that not providing
the change_kind property at all is equivalent to setting
it to the value all.
• drop
Usage:
drop = yes | no
If a function is matched by a suppression specification which
contains the "drop" property set to "yes" (or to "true") then
the function is not even going to be represented in the
internal representation of the ABI being analyzed. This
property makes its enclosing suppression specification to be
applied in the early suppression specification mode. The net
effect is that it potentially reduces the memory used to
represent the ABI being analyzed.
Please note that for this property to be effective, the
enclosing suppression specification must have at least one of
the following properties specified: name_regexp, name,
name_regexp, source_location_not_in or
source_location_not_regexp.
• file_name_not_regexp
Usage:
file_name_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a binary file which name does not match the regular
expression specified as value of this property.
• file_name_regexp
Usage:
file_name_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a binary file which name matches the regular expression
specified as value of this property.
• label
Usage:
label = <some-value>
This property is the same as the label property defined above.
• name
Usage:
name = <some-value>
Suppresses change reports involving functions whose name
equals the value of this property.
• name_not_regexp
Usage:
name_not_regexp = <regular-expression>
Suppresses change reports involving functions whose names
don't match the regular expression specified as value of this
property.
The rules for functions that have several symbol names are the
same rules as for the name_regexp property above.
• name_regexp
Usage:
name_regexp = <regular-expression>
Suppresses change reports involving functions whose name
matches the regular expression specified as value of this
property.
Let's consider the case of functions that have several symbol
names. This happens when the underlying symbol for the
function has aliases. Each symbol name is actually one alias
name.
In this case, if the regular expression matches the name of at
least one of the aliases names, then it must match the names
of all of the aliases of the function for the directive to
actually suppress the diff reports for said function.
• parameter
Usage:
parameter = <function-parameter-specification>
Suppresses change reports involving functions whose parameters
match the parameter specification indicated as value of this
property.
The format of the function parameter specification is:
' <parameter-index> <space> <type-name-or-regular-expression>
That is, an apostrophe followed by a number that is the index
of the parameter, followed by one of several spaces, followed
by either the name of the type of the parameter, or a regular
expression describing a family of parameter type names.
If the parameter type name is designated by a regular
expression, then said regular expression must be enclosed
between two slashes; like /some-regular-expression/.
The index of the first parameter of the function is zero.
Note that for member functions (methods of classes), the this
is the first parameter that comes after the implicit "this"
pointer parameter.
Examples of function parameter specifications are:
'0 int
Which means, the parameter at index 0, whose type name is int.
'4 unsigned char*
Which means, the parameter at index 4, whose type name is
unsigned char*.
'2 /^foo.*&/
Which means, the parameter at index 2, whose type name starts
with the string "foo" and ends with an '&'. In other words,
this is the third parameter and it's a reference on a type
that starts with the string "foo".
• return_type_name
Usage:
return_type_name = <some-value>
Suppresses change reports involving functions whose return
type name equals the value of this property.
• return_type_regexp
Usage:
return_type_regexp = <regular-expression>
Suppresses change reports involving functions whose return
type name matches the regular expression specified as value of
this property.
• soname_regexp
Usage:
soname_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a shared library which SONAME property matches the regular
expression specified as value of this property.
• soname_not_regexp
Usage:
soname_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a shared library which SONAME property does not match the
regular expression specified as value of this property.
• symbol_name
Usage:
symbol_name = <some-value>
Suppresses change reports involving functions whose symbol
name equals the value of this property.
• symbol_name_regexp
Usage:
symbol_name_regexp = <regular-expression>
Suppresses change reports involving functions whose symbol
name matches the regular expression specified as value of this
property.
Let's consider the case of functions that have several symbol
names. This happens when the underlying symbol for the
function has aliases. Each symbol name is actually one alias
name.
In this case, the regular expression must match the names of
all of the aliases of the function for the directive to
actually suppress the diff reports for said function.
• symbol_name_not_regexp
Usage:
symbol_name_not_regexp = <regular-expression>
Suppresses change reports involving functions whose symbol
name does not match the regular expression specified as value
of this property.
• symbol_version
Usage:
symbol_version = <some-value>
Suppresses change reports involving functions whose symbol
version equals the value of this property.
• symbol_version_regexp
Usage:
symbol_version_regexp = <regular-expression>
Suppresses change reports involving functions whose symbol
version matches the regular expression specified as value of
this property.
[suppress_variable]
This directive suppresses report messages about changes on a set
of variables.
Note that for the [suppress_variable] directive to work, at least
one of the following properties must be provided:
label, file_name_regexp, file_name_not_regexp, soname_regexp,
soname_not_regexp, name, name_regexp, name_not_regexp,
symbol_name, symbol_name_regexp, symbol_name_not_regexp,
symbol_version, symbol_version_regexp, type_name,
type_name_regexp.
If none of the above properties are provided, then the
[suppress_variable] directive is simply ignored.
The potential properties of this sections are:
• label
Usage:
label = <some-value>
This property is the same as the label property defined above.
• file_name_regexp
Usage:
file_name_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a binary file which name matches the regular expression
specified as value of this property.
• file_name_not_regexp
Usage:
file_name_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a binary file which name does not match the regular
expression specified as value of this property.
• soname_regexp
Usage:
soname_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a shared library which SONAME property matches the regular
expression specified as value of this property.
• soname_not_regexp
Usage:
soname_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined
in a shared library which SONAME property does not match the
regular expression specified as value of this property.
• name
Usage:
name = <some-value>
Suppresses change reports involving variables whose name
equals the value of this property.
• name_regexp
Usage:
name_regexp = <regular-expression>
Suppresses change reports involving variables whose name
matches the regular expression specified as value of this
property.
• change_kind
Usage:
change_kind = <predefined-possible-values>
Specifies the kind of changes this suppression specification
should apply to. The possible values of this property as well
as their meaning are the same as when it's used in the
[suppress_function] section.
• symbol_name
Usage:
symbol_name = <some-value>
Suppresses change reports involving variables whose symbol
name equals the value of this property.
• symbol_name_regexp
Usage:
symbol_name_regexp = <regular-expression>
Suppresses change reports involving variables whose symbol
name matches the regular expression specified as value of this
property.
• symbol_name_not_regexp
Usage:
symbol_name_not_regexp = <regular-expression>
Suppresses change reports involving variables whose symbol
name does not match the regular expression specified as value
of this property.
• symbol_version
Usage:
symbol_version = <some-value>
Suppresses change reports involving variables whose symbol
version equals the value of this property.
• symbol_version_regexp
Usage:
symbol_version_regexp = <regular-expression>
Suppresses change reports involving variables whose symbol
version matches the regular expression specified as value of
this property.
• type_name
Usage:
type_name = <some-value>
Suppresses change reports involving variables whose type name
equals the value of this property.
• type_name_regexp
Usage:
type_name_regexp = <regular-expression>
Suppresses change reports involving variables whose type name
matches the regular expression specified as value of this
property.
Comments
; or # ASCII character at the beginning of a line indicates a
comment. Comment lines are ignored.
Code examples
1. Suppressing change reports about types.
Suppose we have a library named libtest1-v0.so which contains
this very useful code:
$ cat -n test1-v0.cc
1 // A forward declaration for a type considered to be opaque to
2 // function foo() below.
3 struct opaque_type;
4
5 // This function cannot touch any member of opaque_type. Hence,
6 // changes to members of opaque_type should not impact foo, as far as
7 // ABI is concerned.
8 void
9 foo(opaque_type*)
10 {
11 }
12
13 struct opaque_type
14 {
15 int member0;
16 char member1;
17 };
$
Let's change the layout of struct opaque_type by inserting a data
member around line 15, leading to a new version of the library,
that we shall name libtest1-v1.so:
$ cat -n test1-v1.cc
1 // A forward declaration for a type considered to be opaque to
2 // function foo() below.
3 struct opaque_type;
4
5 // This function cannot touch any member of opaque_type; Hence,
6 // changes to members of opaque_type should not impact foo, as far as
7 // ABI is concerned.
8 void
9 foo(opaque_type*)
10 {
11 }
12
13 struct opaque_type
14 {
15 char added_member; // <-- a new member got added here now.
16 int member0;
17 char member1;
18 };
$
Let's compile both examples. We shall not forget to compile them
with debug information generation turned on:
$ g++ -shared -g -Wall -o libtest1-v0.so test1-v0.cc
$ g++ -shared -g -Wall -o libtest1-v1.so test1-v1.cc
Let's ask abidiff which ABI differences it sees between
libtest1-v0.so and libtest1-v1.so:
$ abidiff libtest1-v0.so libtest1-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void foo(opaque_type*)' has some indirect sub-type changes:
parameter 0 of type 'opaque_type*' has sub-type changes:
in pointed to type 'struct opaque_type':
size changed from 64 to 96 bits
1 data member insertion:
'char opaque_type::added_member', at offset 0 (in bits)
2 data member changes:
'int opaque_type::member0' offset changed from 0 to 32
'char opaque_type::member1' offset changed from 32 to 64
So abidiff reports that the opaque_type's layout has changed in a
significant way, as far as ABI implications are concerned, in
theory. After all, a sub-type (struct opaque_type) of an
exported function (foo()) has seen its layout change. This might
have non negligible ABI implications. But in practice here, the
programmer of the litest1-v1.so library knows that the "soft"
contract between the function foo() and the type struct
opaque_type is to stay away from the data members of the type.
So layout changes of struct opaque_type should not impact foo().
Now to teach abidiff about this soft contract and have it avoid
emitting what amounts to false positives in this case, we write
the suppression specification file below:
$ cat test1.suppr
[suppress_type]
type_kind = struct
name = opaque_type
Translated in plain English, this suppression specification would
read: "Do not emit change reports about a struct which name is
opaque_type".
Let's now invoke abidiff on the two versions of the library
again, but this time with the suppression specification:
$ abidiff --suppressions test1.suppr libtest1-v0.so libtest1-v1.so
Functions changes summary: 0 Removed, 0 Changed (1 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
As you can see, abidiff does not report the change anymore; it
tells us that it was filtered out instead.
Suppressing change reports about types with data member
insertions
Suppose the first version of a library named libtest3-v0.so has
this source code:
/* Compile this with:
gcc -g -Wall -shared -o libtest3-v0.so test3-v0.c
*/
struct S
{
char member0;
int member1; /*
between member1 and member2, there is some padding,
at least on some popular platforms. On
these platforms, adding a small enough data
member into that padding shouldn't change
the offset of member1. Right?
*/
};
int
foo(struct S* s)
{
return s->member0 + s->member1;
}
Now, suppose the second version of the library named
libtest3-v1.so has this source code in which a data member has
been added in the padding space of struct S and another data
member has been added at its end:
/* Compile this with:
gcc -g -Wall -shared -o libtest3-v1.so test3-v1.c
*/
struct S
{
char member0;
char inserted1; /* <---- A data member has been added here... */
int member1;
char inserted2; /* <---- ... and another one has been added here. */
};
int
foo(struct S* s)
{
return s->member0 + s->member1;
}
In libtest3-v1.so, adding char data members S::inserted1 and
S::inserted2 can be considered harmless (from an ABI
compatibility perspective), at least on the x86 platform, because
that doesn't change the offsets of the data members S::member0
and S::member1. But then running abidiff on these two versions
of library yields:
$ abidiff libtest3-v0.so libtest3-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function int foo(S*)' has some indirect sub-type changes:
parameter 0 of type 'S*' has sub-type changes:
in pointed to type 'struct S':
type size changed from 64 to 96 bits
2 data member insertions:
'char S::inserted1', at offset 8 (in bits)
'char S::inserted2', at offset 64 (in bits)
$
That is, abidiff shows us the two changes, even though we (the
developers of that very involved library) know that these changes
are harmless in this particular context.
Luckily, we can devise a suppression specification that
essentially tells abidiff to filter out change reports about
adding a data member between S::member0 and S::member1, and
adding a data member at the end of struct S. We have written
such a suppression specification in a file called test3-1.suppr
and it unsurprisingly looks like:
[suppress_type]
name = S
has_data_member_inserted_between = {offset_after(member0), offset_of(member1)}
has_data_member_inserted_at = end
Now running abidiff with this suppression specification yields:
$ ../build/tools/abidiff --suppressions test3-1.suppr libtest3-v0.so libtest3-v1.so
Functions changes summary: 0 Removed, 0 Changed (1 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
$
Hooora! \o/ (I guess)
Suppressing change reports about types accessed either directly
or through pointers
Suppose we have a first version of an object file which source
code is the file widget-v0.cc below:
// Compile with: g++ -g -c widget-v0.cc
struct widget
{
int x;
int y;
widget()
:x(), y()
{}
};
void
fun0(widget*)
{
// .. do stuff here.
}
void
fun1(widget&)
{
// .. do stuff here ..
}
void
fun2(widget w)
{
// ... do other stuff here ...
}
Now suppose in the second version of that file, named
widget-v1.cc, we have added some data members at the end of the
type struct widget; here is what the content of that file would
look like:
// Compile with: g++ -g -c widget-v1.cc
struct widget
{
int x;
int y;
int w; // We have added these two new data members here ..
int h; // ... and here.
widget()
: x(), y(), w(), h()
{}
};
void
fun0(widget*)
{
// .. do stuff here.
}
void
fun1(widget&)
{
// .. do stuff here ..
}
void
fun2(widget w)
{
// ... do other stuff here ...
}
When we invoke abidiff on the object files resulting from the
compilation of the two file above, here is what we get:
$ abidiff widget-v0.o widget-v1.o
Functions changes summary: 0 Removed, 2 Changed (1 filtered out), 0 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
2 functions with some indirect sub-type change:
[C]'function void fun0(widget*)' has some indirect sub-type changes:
parameter 1 of type 'widget*' has sub-type changes:
in pointed to type 'struct widget':
type size changed from 64 to 128 bits
2 data member insertions:
'int widget::w', at offset 64 (in bits)
'int widget::h', at offset 96 (in bits)
[C]'function void fun2(widget)' has some indirect sub-type changes:
parameter 1 of type 'struct widget' has sub-type changes:
details were reported earlier
$
I guess a little bit of explaining is due here. abidiff detects
that two data member got added at the end of struct widget. it
also tells us that the type change impacts the exported function
fun0() which uses the type struct widget through a pointer, in
its signature.
Careful readers will notice that the change to struct widget also
impacts the exported function fun1(), that uses type struct
widget through a reference. But then abidiff doesn't tell us
about the impact on that function fun1() because it has evaluated
that change as being redundant with the change it reported on
fun0(). It has thus filtered it out, to avoid cluttering the
output with noise.
Redundancy detection and filtering is fine and helpful to avoid
burying the important information in a sea of noise. However, it
must be treated with care, by fear of mistakenly filtering out
relevant and important information.
That is why abidiff tells us about the impact that the change to
struct widget has on function fun2(). In this case, that
function uses the type struct widget directly (in its signature).
It does not use it via a pointer or a reference. In this case,
the direct use of this type causes fun2() to be exposed to a
potentially harmful ABI change. Hence, the report about fun2()
is not filtered out, even though it's about that same change on
struct widget.
To go further in suppressing reports about changes that are
harmless and keeping only those that we know are harmful, we
would like to go tell abidiff to suppress reports about this
particular struct widget change when it impacts uses of struct
widget through a pointer or reference. In other words, suppress
the change reports about fun0() and fun1(). We would then write
this suppression specification, in file widget.suppr:
[suppress_type]
name = widget
type_kind = struct
has_data_member_inserted_at = end
accessed_through = reference-or-pointer
# So this suppression specification says to suppress reports about
# the type 'struct widget', if this type was added some data member
# at its end, and if the change impacts uses of the type through a
# reference or a pointer.
Invoking abidiff on widget-v0.o and widget-v1.o with this
suppression specification yields:
$ abidiff --suppressions widget.suppr widget-v0.o widget-v1.o
Functions changes summary: 0 Removed, 1 Changed (2 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void fun2(widget)' has some indirect sub-type changes:
parameter 1 of type 'struct widget' has sub-type changes:
type size changed from 64 to 128 bits
2 data member insertions:
'int widget::w', at offset 64 (in bits)
'int widget::h', at offset 96 (in bits)
$
As expected, I guess.
Suppressing change reports about functions.
Suppose we have a first version a library named libtest2-v0.so
whose source code is:
$ cat -n test2-v0.cc
1 struct S1
2 {
3 int m0;
4
5 S1()
6 : m0()
7 {}
8 };
9
10 struct S2
11 {
12 int m0;
13
14 S2()
15 : m0()
16 {}
17 };
18
19 struct S3
20 {
21 int m0;
22
23 S3()
24 : m0()
25 {}
26 };
27
28 int
29 func(S1&)
30 {
31 // suppose the code does something with the argument.
32 return 0;
33
34 }
35
36 char
37 func(S2*)
38 {
39 // suppose the code does something with the argument.
40 return 0;
41 }
42
43 unsigned
44 func(S3)
45 {
46 // suppose the code does something with the argument.
47 return 0;
48 }
$
And then we come up with a second version libtest2-v1.so of that
library; the source code is modified by making the structures S1,
S2, S3 inherit another struct:
$ cat -n test2-v1.cc
1 struct base_type
2 {
3 int m_inserted;
4 };
5
6 struct S1 : public base_type // <--- S1 now has base_type as its base
7 // type.
8 {
9 int m0;
10
11 S1()
12 : m0()
13 {}
14 };
15
16 struct S2 : public base_type // <--- S2 now has base_type as its base
17 // type.
18 {
19 int m0;
20
21 S2()
22 : m0()
23 {}
24 };
25
26 struct S3 : public base_type // <--- S3 now has base_type as its base
27 // type.
28 {
29 int m0;
30
31 S3()
32 : m0()
33 {}
34 };
35
36 int
37 func(S1&)
38 {
39 // suppose the code does something with the argument.
40 return 0;
41
42 }
43
44 char
45 func(S2*)
46 {
47 // suppose the code does something with the argument.
48 return 0;
49 }
50
51 unsigned
52 func(S3)
53 {
54 // suppose the code does something with the argument.
55 return 0;
56 }
$
Now let's build the two libraries:
g++ -Wall -g -shared -o libtest2-v0.so test2-v0.cc
g++ -Wall -g -shared -o libtest2-v0.so test2-v0.cc
Let's look at the output of abidiff:
$ abidiff libtest2-v0.so libtest2-v1.so
Functions changes summary: 0 Removed, 3 Changed, 0 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
3 functions with some indirect sub-type change:
[C]'function unsigned int func(S3)' has some indirect sub-type changes:
parameter 0 of type 'struct S3' has sub-type changes:
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S3::m0' offset changed from 0 to 32
[C]'function char func(S2*)' has some indirect sub-type changes:
parameter 0 of type 'S2*' has sub-type changes:
in pointed to type 'struct S2':
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S2::m0' offset changed from 0 to 32
[C]'function int func(S1&)' has some indirect sub-type changes:
parameter 0 of type 'S1&' has sub-type changes:
in referenced type 'struct S1':
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S1::m0' offset changed from 0 to 32
$
Let's tell abidiff to avoid showing us the differences on the
overloads of func that takes either a pointer or a reference.
For that, we author this simple suppression specification:
$ cat -n libtest2.suppr
1 [suppress_function]
2 name = func
3 parameter = '0 S1&
4
5 [suppress_function]
6 name = func
7 parameter = '0 S2*
$
And then let's invoke abidiff with the suppression specification:
$ ../build/tools/abidiff --suppressions libtest2.suppr libtest2-v0.so libtest2-v1.so
Functions changes summary: 0 Removed, 1 Changed (2 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function unsigned int func(S3)' has some indirect sub-type changes:
parameter 0 of type 'struct S3' has sub-type changes:
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S3::m0' offset changed from 0 to 32
The suppression specification could be reduced using regular
expressions:
$ cat -n libtest2-1.suppr
1 [suppress_function]
2 name = func
3 parameter = '0 /^S.(&|\\*)/
$
$ ../build/tools/abidiff --suppressions libtest2-1.suppr libtest2-v0.so libtest2-v1.so
Functions changes summary: 0 Removed, 1 Changed (2 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function unsigned int func(S3)' has some indirect sub-type changes:
parameter 0 of type 'struct S3' has sub-type changes:
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S3::m0' offset changed from 0 to 32
$
Dodji Seketeli
2014-2022, Red Hat, Inc.
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Instrumentation Library) project. Information about the project
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