malloc_usable_size - obtain size of block of memory allocated from heap
size_t malloc_usable_size (void *ptr);
() function returns the number of usable bytes in
the block pointed to by ptr
, a pointer to a block of memory allocated
or a related function.
() returns the number of usable bytes in the block of
allocated memory pointed to by ptr
. If ptr
is NULL, 0 is
Multithreading (see pthreads(7))¶
() function is thread-safe.
This function is a GNU extension.
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.
This page is part of release 3.74 of the Linux man-pages
description of the project, information about reporting bugs, and the latest
version of this page, can be found at