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NAME | SYNOPSIS | DESCRIPTION | VERSIONS | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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void(3type) void(3type)
void - abstract type
void *
A pointer to any object type may be converted to a pointer to
void and back. POSIX further requires that any pointer,
including pointers to functions, may be converted to a pointer to
void and back.
Conversions from and to any other pointer type are done
implicitly, not requiring casts at all. Note that this feature
prevents any kind of type checking: the programmer should be
careful not to convert a void * value to a type incompatible to
that of the underlying data, because that would result in
undefined behavior.
This type is useful in function parameters and return value to
allow passing values of any type. The function will typically
use some mechanism to know the real type of the data being passed
via a pointer to void.
A value of this type can't be dereferenced, as it would give a
value of type void, which is not possible. Likewise, pointer
arithmetic is not possible with this type. However, in GNU C,
pointer arithmetic is allowed as an extension to the standard;
this is done by treating the size of a void or of a function as
1. A consequence of this is that sizeof is also allowed on void
and on function types, and returns 1.
Use with printf(3) and scanf(3)
The conversion specifier for void * for the printf(3) and the
scanf(3) families of functions is p.
The POSIX requirement about compatibility between void * and
function pointers was added in POSIX.1-2008 Technical Corrigendum
1 (2013).
C11, POSIX.1-2008.
C89, POSIX.1-2001.
malloc(3), memcmp(3), memcpy(3), memset(3), intptr_t(3type)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. 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
Linux man-pages 6.9.1 2024-05-02 void(3type)
Pages that refer to this page: NULL(3const)
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HTML rendering created 2024-06-26 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. |
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