malloc_usable_size(3) Library Functions Manual malloc_usable_size(3) 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 *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 at- tributes(7). ┌────────────────────────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├────────────────────────────────────────────┼───────────────┼─────────┤ │malloc_usable_size() │ Thread safety │ MT-Safe │ └────────────────────────────────────────────┴───────────────┴─────────┘ STANDARDS This function is a GNU extension. NOTES The value returned by malloc_usable_size() may be greater than the re- quested size of the allocation because of alignment and minimum size constraints. Although the excess bytes can be overwritten by the ap- plication 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) Linux man-pages 6.03 2022-12-15 malloc_usable_size(3)
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