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 attributes(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
       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 5.09 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                                2017-09-15              MALLOC_USABLE_SIZE(3)