github.com/afumu/libc@v0.0.6/musl/src/malloc/oldmalloc/malloc_usable_size.c (about)

     1  #include <malloc.h>
     2  #include "malloc_impl.h"
     3   
     4  hidden void *(*const __realloc_dep)(void *, size_t) = realloc;
     5  
     6  size_t malloc_usable_size(void *p)
     7  {
     8  	return p ? CHUNK_SIZE(MEM_TO_CHUNK(p)) - OVERHEAD : 0;
     9  }