malloc_usable_size

MALLOC_USABLE_SIZE(3)      Linux Programmer's Manual     MALLOC_USABLE_SIZE(3)

NAME
       malloc_usable_size - obtain size of block of memory allocated from heap

SYNOPSIS
       #include <malloc.h>

       size_t malloc_usable_size (void *ptr);

DESCRIPTION
       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.

RETURN VALUE
       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.

ATTRIBUTES
       For an  explanation  of  the  terms  used  in  this  section,  see  at-
       tributes(7).

       +---------------------+---------------+---------+
       |Interface            | Attribute     | Value   |
       +---------------------+---------------+---------+
       |malloc_usable_size() | Thread safety | MT-Safe |
       +---------------------+---------------+---------+
CONFORMING TO
       This function is a GNU extension.

NOTES
       The  value returned by malloc_usable_size() may be greater than the re-
       quested size of the allocation because of alignment  and  minimum  size
       constraints.   Although  the excess bytes can be overwritten by the ap-
       plication 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.

SEE ALSO
       malloc(3)

COLOPHON
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       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.

GNU                               2017-09-15             MALLOC_USABLE_SIZE(3)