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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | CAVEATS | SEE ALSO | COLOPHON |
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malloc_usable_size(3) Library Functions Manual malloc_usable_size(3)
malloc_usable_size - obtain size of block of memory allocated from
heap
Standard C library (libc, -lc)
#include <malloc.h>
size_t malloc_usable_size(void *_Nullable ptr);
This function can be used for diagnostics or statistics about
allocations from malloc(3) or a related function.
malloc_usable_size() returns a value no less than the size of the
block of allocated memory pointed to by ptr. If ptr is NULL, 0 is
returned.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ malloc_usable_size() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
GNU.
The value returned by malloc_usable_size() may be greater than the
requested size of the allocation because of various internal
implementation details, none of which the programmer should rely
on. This function is intended to only be used for diagnostics and
statistics; writing to the excess memory without first calling
realloc(3) to resize the allocation is not supported. The
returned value is only valid at the time of the call.
malloc(3)
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-6.15.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-
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man-pages@man7.org
Linux man-pages 6.15 2025-05-17 malloc_usable_size(3)
Pages that refer to this page: malloc(3)
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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. |
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