if we look at the malloc function written in malloc.h, we have the answer to this.

see.
https://github.com/lattera/glibc/blob/895ef79e04a953cac1493863bcae29ad85657ee1/malloc/malloc.c#L487

/*
  malloc(size_t n)
  Returns a pointer to a newly allocated chunk of at least n bytes, or null
  if no space is available. Additionally, on failure, errno is
  set to ENOMEM on ANSI C systems.

  If n is zero, malloc returns a minumum-sized chunk. (The minimum
  size is 16 bytes on most 32bit systems, and 24 or 32 bytes on 64bit
  systems.)  On most systems, size_t is an unsigned type, so calls
  with negative arguments are interpreted as requests for huge amounts
  of space, which will often fail. The maximum supported value of n
  differs across systems, but is in all cases less than the maximum
  representable value of a size_t.
*/
void*  __libc_malloc(size_t);
libc_hidden_proto (__libc_malloc)