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malloc_usable_size

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

malloc_usable_size - obtain size of block of memory allocated from heap

LIBRARY

Standard C library (libc,~-lc)

SYNOPSIS

#include <malloc.h>
size_t malloc_usable_size(void *_Nullable ptr);

DESCRIPTION

This function can be used for diagnostics or statistics about allocations from malloc(3) or a related function.

RETURN VALUE

malloc_usable_size() returns a value no less than the size of 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	M-Safe

STANDARDS

GNU.

CAVEATS

The value returned by malloc_usable_size() may be greater than the requested size of the allocation because of various internal implementation details, none of which the programmer should rely on. This function is intended to only be used for diagnostics and statistics; writing to the excess memory without first calling realloc(3) to resize the allocation is not supported. The returned value is only valid at the time of the call.