malloc_usable_size(3) — Linux manual page


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

NAME         top

       malloc_usable_size - obtain size of block of memory allocated
       from heap

SYNOPSIS         top

       #include <malloc.h>

       size_t malloc_usable_size(void *ptr);

DESCRIPTION         top

       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         top

       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         top

       For an explanation of the terms used in this section, see

       │Interface                             Attribute     Value   │
       │malloc_usable_size()                  │ Thread safety │ MT-Safe │

CONFORMING TO         top

       This function is a GNU extension.

NOTES         top

       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         top


COLOPHON         top

       This page is part of release 5.13 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

GNU                            2021-03-22          MALLOC_USABLE_SIZE(3)

Pages that refer to this page: malloc(3)