malloc_usable_size(3) — Linux manual page

malloc_usable_size(3)   Library Functions Manual   malloc_usable_size(3)

NAME

       malloc_usable_size - obtain size of block of memory allocated
       from heap

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <malloc.h>

       size_t malloc_usable_size(void *_Nullable ptr);

DESCRIPTION

       This function can be used for diagnostics or statistics about
       allocations from malloc(3) or a related function.

RETURN VALUE

       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.

ATTRIBUTES

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌─────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                           │ Attribute     │ Value   │
       ├─────────────────────────────────────┼───────────────┼─────────┤
       │ malloc_usable_size()                │ Thread safety │ MT-Safe │
       └─────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       GNU.

CAVEATS

       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.

SEE ALSO

       malloc(3)

COLOPHON

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Linux man-pages 6.9.1          2024-05-02          malloc_usable_size(3)

Pages that refer to this page: malloc(3)

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