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

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