|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
PCRE2BUILD(3) Library Functions Manual PCRE2BUILD(3)
PCRE2 - Perl-compatible regular expressions (revised API)
PCRE2 is distributed with a configure script that can be used to
build the library in Unix-like environments using the Autotools
applications. Also in the distribution are files to support
building using CMake instead of configure. The text file README
contains general information about building with Autotools (some
of which is repeated below), and also has some comments about
building on various operating systems. The files in the vms
directory support building under OpenVMS. There is a lot more
information about building PCRE2 without using Autotools
(including information about using CMake and building "by hand")
in the text file called NON-AUTOTOOLS-BUILD. You should consult
this file as well as the README file if you are building in a non-
Unix-like environment.
The rest of this document describes the optional features of PCRE2
that can be selected when the library is compiled. It assumes use
of the configure script, where the optional features are selected
or deselected by providing options to configure before running the
make command. However, the same options can be selected in both
Unix-like and non-Unix-like environments if you are using CMake
instead of configure to build PCRE2.
If you are not using Autotools or CMake, option selection can be
done by editing the config.h file, or by passing parameter
settings to the compiler, as described in NON-AUTOTOOLS-BUILD.
The complete list of options for configure (which includes the
standard ones such as the selection of the installation directory)
can be obtained by running
./configure --help
The following sections include descriptions of "on/off" options
whose names begin with --enable or --disable. Because of the way
that configure works, --enable and --disable always come in pairs,
so the complementary option always exists as well, but as it
specifies the default, it is not described. Options that specify
values have names that start with --with. At the end of a
configure run, a summary of the configuration is output.
By default, a library called libpcre2-8 is built, containing
functions that take string arguments contained in arrays of bytes,
interpreted either as single-byte characters, or UTF-8 strings.
You can also build two other libraries, called libpcre2-16 and
libpcre2-32, which process strings that are contained in arrays of
16-bit and 32-bit code units, respectively. These can be
interpreted either as single-unit characters or UTF-16/UTF-32
strings. To build these additional libraries, add one or both of
the following to the configure command:
--enable-pcre2-16
--enable-pcre2-32
If you do not want the 8-bit library, add
--disable-pcre2-8
as well. At least one of the three libraries must be built. Note
that the POSIX wrapper is for the 8-bit library only, and that
pcre2grep is an 8-bit program. Neither of these are built if you
select only the 16-bit or 32-bit libraries.
The Autotools PCRE2 building process uses libtool to build both
shared and static libraries by default. You can suppress an
unwanted library by adding one of
--disable-shared
--disable-static
to the configure command. Setting --disable-shared ensures that
PCRE2 libraries are built as static libraries. The binaries that
are then created as part of the build process (for example,
pcre2test and pcre2grep) are linked statically with one or more
PCRE2 libraries, but may also be dynamically linked with other
libraries such as libc. If you want these binaries to be fully
statically linked, you can set LDFLAGS like this:
LDFLAGS=--static ./configure --disable-shared
Note the two hyphens in --static. Of course, this works only if
static versions of all the relevant libraries are available for
linking.
By default, PCRE2 is built with support for Unicode and UTF
character strings. To build it without Unicode support, add
--disable-unicode
to the configure command. This setting applies to all three
libraries. It is not possible to build one library with Unicode
support and another without in the same configuration.
Of itself, Unicode support does not make PCRE2 treat strings as
UTF-8, UTF-16 or UTF-32. To do that, applications that use the
library can set the PCRE2_UTF option when they call
pcre2_compile() to compile a pattern. Alternatively, patterns may
be started with (*UTF) unless the application has locked this out
by setting PCRE2_NEVER_UTF.
UTF support allows the libraries to process character code points
up to 0x10ffff in the strings that they handle. Unicode support
also gives access to the Unicode properties of characters, using
pattern escapes such as \P, \p, and \X. Only the general category
properties such as Lu and Nd, script names, and some bi-
directional properties are supported. Details are given in the
pcre2pattern documentation.
Pattern escapes such as \d and \w do not by default make use of
Unicode properties. The application can request that they do by
setting the PCRE2_UCP option. Unless the application has set
PCRE2_NEVER_UCP, a pattern may also request this by starting with
(*UCP).
The \C escape sequence, which matches a single code unit, even in
a UTF mode, can cause unpredictable behaviour because it may leave
the current matching point in the middle of a multi-code-unit
character. The application can lock it out by setting the
PCRE2_NEVER_BACKSLASH_C option when calling pcre2_compile(). There
is also a build-time option
--enable-never-backslash-C
(note the upper case C) which locks out the use of \C entirely.
Just-in-time (JIT) compiler support is included in the build by
specifying
--enable-jit
This support is available only for certain hardware architectures.
If this option is set for an unsupported architecture, a building
error occurs. If in doubt, use
--enable-jit=auto
which enables JIT only if the current hardware is supported. You
can check if JIT is enabled in the configuration summary that is
output at the end of a configure run. If you are enabling JIT
under SELinux you may also want to add
--enable-jit-sealloc
which enables the use of an execmem allocator in JIT that is
compatible with SELinux. This has no effect if JIT is not enabled.
See the pcre2jit documentation for a discussion of JIT usage. When
JIT support is enabled, pcre2grep automatically makes use of it,
unless you add
--disable-pcre2grep-jit
to the configure command.
By default, PCRE2 interprets the linefeed (LF) character as
indicating the end of a line. This is the normal newline character
on Unix-like systems. You can compile PCRE2 to use carriage return
(CR) instead, by adding
--enable-newline-is-cr
to the configure command. There is also an --enable-newline-is-lf
option, which explicitly specifies linefeed as the newline
character.
Alternatively, you can specify that line endings are to be
indicated by the two-character sequence CRLF (CR immediately
followed by LF). If you want this, add
--enable-newline-is-crlf
to the configure command. There is a fourth option, specified by
--enable-newline-is-anycrlf
which causes PCRE2 to recognize any of the three sequences CR, LF,
or CRLF as indicating a line ending. A fifth option, specified by
--enable-newline-is-any
causes PCRE2 to recognize any Unicode newline sequence. The
Unicode newline sequences are the three just mentioned, plus the
single characters VT (vertical tab, U+000B), FF (form feed,
U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and
PS (paragraph separator, U+2029). The final option is
--enable-newline-is-nul
which causes NUL (binary zero) to be set as the default line-
ending character.
Whatever default line ending convention is selected when PCRE2 is
built can be overridden by applications that use the library. At
build time it is recommended to use the standard for your
operating system.
By default, the sequence \R in a pattern matches any Unicode
newline sequence, independently of what has been selected as the
line ending sequence. If you specify
--enable-bsr-anycrlf
the default is changed so that \R matches only CR, LF, or CRLF.
Whatever is selected when PCRE2 is built can be overridden by
applications that use the library.
Within a compiled pattern, offset values are used to point from
one part to another (for example, from an opening parenthesis to
an alternation metacharacter). By default, in the 8-bit and 16-bit
libraries, two-byte values are used for these offsets, leading to
a maximum size for a compiled pattern of around 64 thousand code
units. This is sufficient to handle all but the most gigantic
patterns. Nevertheless, some people do want to process truly
enormous patterns, so it is possible to compile PCRE2 to use
three-byte or four-byte offsets by adding a setting such as
--with-link-size=3
to the configure command. The value given must be 2, 3, or 4. For
the 16-bit library, a value of 3 is rounded up to 4. In these
libraries, using longer offsets slows down the operation of PCRE2
because it has to load additional data when handling them. For the
32-bit library the value is always 4 and cannot be overridden; the
value of --with-link-size is ignored.
The pcre2_match() function increments a counter each time it goes
round its main loop. Putting a limit on this counter controls the
amount of computing resource used by a single call to
pcre2_match(). The limit can be changed at run time, as described
in the pcre2api documentation. The default is 10 million, but this
can be changed by adding a setting such as
--with-match-limit=500000
to the configure command. This setting also applies to the
pcre2_dfa_match() matching function, and to JIT matching (though
the counting is done differently).
The pcre2_match() function uses heap memory to record backtracking
points. The more nested backtracking points there are (that is,
the deeper the search tree), the more memory is needed. There is
an upper limit, specified in kibibytes (units of 1024 bytes). This
limit can be changed at run time, as described in the pcre2api
documentation. The default limit (in effect unlimited) is 20
million. You can change this by a setting such as
--with-heap-limit=500
which limits the amount of heap to 500 KiB. This limit applies
only to interpretive matching in pcre2_match() and
pcre2_dfa_match(), which may also use the heap for internal
workspace when processing complicated patterns. This limit does
not apply when JIT (which has its own memory arrangements) is
used.
You can also explicitly limit the depth of nested backtracking in
the pcre2_match() interpreter. This limit defaults to the value
that is set for --with-match-limit. You can set a lower default
limit by adding, for example,
--with-match-limit-depth=10000
to the configure command. This value can be overridden at run
time. This depth limit indirectly limits the amount of heap memory
that is used, but because the size of each backtracking "frame"
depends on the number of capturing parentheses in a pattern, the
amount of heap that is used before the limit is reached varies
from pattern to pattern. This limit was more useful in versions
before 10.30, where function recursion was used for backtracking.
As well as applying to pcre2_match(), the depth limit also
controls the depth of recursive function calls in
pcre2_dfa_match(). These are used for lookaround assertions,
atomic groups, and recursion within patterns. The limit does not
apply to JIT matching.
Lookbehind assertions in which one or more branches can match a
variable number of characters are supported only if there is a
maximum matching length for each top-level branch. There is a
limit to this maximum that defaults to 255 characters. You can
alter this default by a setting such as
--with-max-varlookbehind=100
The limit can be changed at runtime by calling
pcre2_set_max_varlookbehind(). Lookbehind assertions in which
every branch matches a fixed number of characters (not necessarily
all the same) are not constrained by this limit.
PCRE2 uses fixed tables for processing characters whose code
points are less than 256. By default, PCRE2 is built with a set of
tables that are distributed in the file
src/pcre2_chartables.c.dist. These tables are for ASCII codes
only. If you add
--enable-rebuild-chartables
to the configure command, the distributed tables are no longer
used. Instead, a program called pcre2_dftables is compiled and
run. This outputs the source for new set of tables, created in the
default locale of your C run-time system. This method of replacing
the tables does not work if you are cross compiling, because
pcre2_dftables needs to be run on the local host and therefore not
compiled with the cross compiler.
If you need to create alternative tables when cross compiling, you
will have to do so "by hand". There may also be other reasons for
creating tables manually. To cause pcre2_dftables to be built on
the local host, run a normal compiling command, and then run the
program with the output file as its argument, for example:
cc src/pcre2_dftables.c -o pcre2_dftables
./pcre2_dftables src/pcre2_chartables.c
This builds the tables in the default locale of the local host. If
you want to specify a locale, you must use the -L option:
LC_ALL=fr_FR ./pcre2_dftables -L src/pcre2_chartables.c
You can also specify -b (with or without -L). This causes the
tables to be written in binary instead of as source code. A set of
binary tables can be loaded into memory by an application and
passed to pcre2_compile() in the same way as tables created by
calling pcre2_maketables(). The tables are just a string of bytes,
independent of hardware characteristics such as endianness. This
means they can be bundled with an application that runs in
different environments, to ensure consistent behaviour.
PCRE2 assumes by default that it will run in an environment where
the character code is ASCII or Unicode, which is a superset of
ASCII. This is the case for most computer operating systems. PCRE2
can, however, be compiled to run in an 8-bit EBCDIC environment by
adding
--enable-ebcdic --disable-unicode
to the configure command. You should only use it if you know that
you are in an EBCDIC environment (for example, an IBM mainframe
operating system).
This setting implies --enable-rebuild-chartables, in order to
ensure that you have the correct default character tables for your
system's codepage. There is an exception when you set --enable-
ebcdic-ignoring-compiler (see below), which allows using a default
set of EBCDIC 1047 character tables rather than forcing use of
--enable-rebuild-chartables.
It is not supported to enable both EBCDIC input and either ASCII
or UTF-8/16/32 in the same build of the library. When PCRE2 is
built with EBCDIC support, it always operates in EBCDIC, and
consequently --enable-unicode and --enable-ebcdic are mutually
exclusive.
The EBCDIC character that corresponds to an ASCII LF is assumed to
have the value 0x15 by default. However, in some EBCDIC
environments, 0x25 is used. In such an environment you should use
--enable-ebcdic-nl25
(which implies --enable-ebcdic). The EBCDIC character for CR has
the same value as in ASCII, namely, 0x0d. Whichever of 0x15 and
0x25 is not chosen as LF is made to correspond to the Unicode NEL
character (which, in Unicode, is 0x85).
The options that select newline behaviour, such as --enable-
newline-is-cr, and equivalent run-time options, refer to these
character values in an EBCDIC environment.
On systems requiring an EBCDIC build of PCRE2, the compiler should
be set to use the correct codepage, so that C character literals
such as 'z' use the correct numeric value for whichever EBCDIC
codpage is in use. (PCRE2 cannot support multiple EBCDIC codepages
dynamically.) However, if this not possible, then you can use
--enable-ebcdic-ignoring-compiler
in order to disregard the compiler's codepage, and instead force
PCRE2 to use numeric constants corresponding to the EBCDIC 1047
codepage instead. This can be used to build (or test) EBCDIC
support on an ASCII/UTF-8 system such as Linux.
By default pcre2grep supports the use of callouts with string
arguments within the patterns it is matching. There are two kinds:
one that generates output using local code, and another that calls
an external program or script. If --disable-pcre2grep-callout-
fork is added to the configure command, only the first kind of
callout is supported; if --disable-pcre2grep-callout is used, all
callouts are completely ignored. For more details of pcre2grep
callouts, see the pcre2grep documentation.
By default, pcre2grep reads all files as plain text. You can build
it so that it recognizes files whose names end in .gz or .bz2, and
reads them with libz or libbz2, respectively, by adding one or
both of
--enable-pcre2grep-libz
--enable-pcre2grep-libbz2
to the configure command. These options naturally require that the
relevant libraries are installed on your system. Configuration
will fail if they are not.
pcre2grep uses an internal buffer to hold a "window" on the file
it is scanning, in order to be able to output "before" and "after"
lines when it finds a match. The default starting size of the
buffer is 20KiB. The buffer itself is three times this size, but
because of the way it is used for holding "before" lines, the
longest line that is guaranteed to be processable is the notional
buffer size. If a longer line is encountered, pcre2grep
automatically expands the buffer, up to a specified maximum size,
whose default is 1MiB or the starting size, whichever is the
larger. You can change the default parameter values by adding, for
example,
--with-pcre2grep-bufsize=51200
--with-pcre2grep-max-bufsize=2097152
to the configure command. The caller of pcre2grep can override
these values by using --buffer-size and --max-buffer-size on the
command line.
If you add one of
--enable-pcre2test-libreadline
--enable-pcre2test-libedit
to the configure command, pcre2test is linked with the libreadline
orlibedit library, respectively, and when its input is from a
terminal, it reads it using the readline() function. This provides
line-editing and history facilities. Note that libreadline is GPL-
licensed, so if you distribute a binary of pcre2test linked in
this way, there may be licensing issues. These can be avoided by
linking instead with libedit, which has a BSD licence.
Setting --enable-pcre2test-libreadline causes the -lreadline
option to be added to the pcre2test build. In many operating
environments with a system-installed readline library this is
sufficient. However, in some environments (e.g. if an unmodified
distribution version of readline is in use), some extra
configuration may be necessary. The INSTALL file for libreadline
says this:
"Readline uses the termcap functions, but does not link with
the termcap or curses library itself, allowing applications
which link with readline the to choose an appropriate library."
If your environment has not been set up so that an appropriate
library is automatically included, you may need to add something
like
LIBS="-ncurses"
immediately before the configure command.
If you add
--enable-debug
to the configure command, additional debugging code is included in
the build. This feature is intended for use by the PCRE2
maintainers.
If you add
--enable-valgrind
to the configure command, PCRE2 will use valgrind annotations to
mark certain memory regions as unaddressable. This allows it to
detect invalid memory accesses, and is mostly useful for debugging
PCRE2 itself.
If your C compiler is gcc, you can build a version of PCRE2 that
can generate a code coverage report for its test suite. To enable
this, you must install lcov version 1.6 or above. Then specify
--enable-coverage
to the configure command and build PCRE2 in the usual way.
Note that using ccache (a caching C compiler) is incompatible with
code coverage reporting. If you have configured ccache to run
automatically on your system, you must set the environment
variable
CCACHE_DISABLE=1
before running make to build PCRE2, so that ccache is not used.
When --enable-coverage is used, the following addition targets are
added to the Makefile:
make coverage
This creates a fresh coverage report for the PCRE2 test suite. It
is equivalent to running "make coverage-reset", "make coverage-
baseline", "make check", and then "make coverage-report".
make coverage-reset
This zeroes the coverage counters, but does nothing else.
make coverage-baseline
This captures baseline coverage information.
make coverage-report
This creates the coverage report.
make coverage-clean-report
This removes the generated coverage report without cleaning the
coverage data itself.
make coverage-clean-data
This removes the captured coverage data without removing the
coverage files created at compile time (*.gcno).
make coverage-clean
This cleans all coverage data including the generated coverage
report. For more information about code coverage, see the gcov and
lcov documentation.
The C99 standard defines formatting modifiers z and t for size_t
and ptrdiff_t values, respectively. By default, PCRE2 uses these
modifiers in environments other than old versions of Microsoft
Visual Studio when __STDC_VERSION__ is defined and has a value
greater than or equal to 199901L (indicating support for C99).
However, there is at least one environment that claims to be C99
but does not support these modifiers. If
--disable-percent-zt
is specified, no use is made of the z or t modifiers. Instead of
%td or %zu, a suitable format is used depending in the size of
long for the platform.
There is a special option for use by people who want to run
fuzzing tests on PCRE2:
--enable-fuzz-support
At present this applies only to the 8-bit library. If set, it
causes an extra library called libpcre2-fuzzsupport.a to be built,
but not installed. This contains a single function called
LLVMFuzzerTestOneInput() whose arguments are a pointer to a string
and the length of the string. When called, this function tries to
compile the string as a pattern, and if that succeeds, to match
it. This is done both with no options and with some random
options bits that are generated from the string.
Setting --enable-fuzz-support also causes a binary called
pcre2fuzzcheck to be created. This is normally run under valgrind
or used when PCRE2 is compiled with address sanitizing enabled. It
calls the fuzzing function and outputs information about what it
is doing. The input strings are specified by arguments: if an
argument starts with "=" the rest of it is a literal input string.
Otherwise, it is assumed to be a file name, and the contents of
the file are the test string.
In versions of PCRE2 prior to 10.30, there were two ways of
handling backtracking in the pcre2_match() function. The default
was to use the system stack, but if
--disable-stack-for-recursion
was set, memory on the heap was used. From release 10.30 onwards
this has changed (the stack is no longer used) and this option now
does nothing except give a warning.
pcre2api(3), pcre2-config(3).
Philip Hazel
Retired from University Computing Service
Cambridge, England.
Last updated: 16 April 2024
Copyright (c) 1997-2024 University of Cambridge.
This page is part of the PCRE (Perl Compatible Regular
Expressions) project. Information about the project can be found
at ⟨http://www.pcre.org/⟩. If you have a bug report for this
manual page, see
⟨http://bugs.exim.org/enter_bug.cgi?product=PCRE⟩. This page was
obtained from the tarball fetched from
⟨https://github.com/PhilipHazel/pcre2.git⟩ on 2025-08-11. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
PCRE2 10.46-DEV 16 April 2024 PCRE2BUILD(3)
Pages that refer to this page: pcre2api(3)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|