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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
MALLOC_USABLE_SIZE(3) Linux Programmer's Manual MALLOC_USABLE_SIZE(3)
malloc_usable_size - obtain size of block of memory allocated from
heap
#include <malloc.h>
size_t malloc_usable_size (void *ptr);
The malloc_usable_size() function returns the number of usable bytes
in the block pointed to by ptr, a pointer to a block of memory
allocated by malloc(3) or a related function.
malloc_usable_size() returns the number of usable bytes in 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 │
└─────────────────────┴───────────────┴─────────┘
This function is a GNU extension.
The value returned by malloc_usable_size() may be greater than the
requested size of the allocation because of alignment and minimum
size constraints. Although the excess bytes can be overwritten by
the application without ill effects, this is not good programming
practice: the number of excess bytes in an allocation depends on the
underlying implementation.
The main use of this function is for debugging and introspection.
malloc(3)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
GNU 2015-03-02 MALLOC_USABLE_SIZE(3)
Pages that refer to this page: malloc(3)