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
   Multithreading (see pthreads(7))
       The malloc_usable_size() function is thread-safe.

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  implemen‐
       tation.

       The main use of this function is for debugging and introspection.

SEE ALSO
       malloc(3)

COLOPHON
       This  page  is  part of release 3.74 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 http://www.kernel.org/doc/man-pages/.



GNU                                         2014-06-13                      MALLOC_USABLE_SIZE(3)