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NAME |SYNOPSIS |DESCRIPTION |VERSIONS |STANDARDS |HISTORY |SEE ALSO |COLOPHON | |
void(3type)void(3type)void - abstract type
void *
A pointer to any object type may be converted to a pointer tovoid and back. POSIX further requires that any pointer, including pointers to functions, may be converted to a pointer tovoid 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 avoid * 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 tovoid. A value of this type can't be dereferenced, as it would give a value of typevoid, 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 avoid or of a function as 1. A consequence of this is thatsizeof is also allowed onvoid and on function types, and returns 1.Use with printf(3) and scanf(3) The conversion specifier forvoid * for theprintf(3) and thescanf(3) families of functions isp.
The POSIX requirement about compatibility betweenvoid * 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 theman-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-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ 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 isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17void(3type)Pages that refer to this page:NULL(3const)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |