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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.
CONFORMING TO
       This function is a GNU extension.
NOTES
       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.
SEE ALSO
       malloc(3)
COLOPHON
       This  page  is  part of release 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU                               2012-03-29             MALLOC_USABLE_SIZE(3)