[PATCH] string: Add tests for zero length string inputs

[Paul Eggert]

On 09/22/2014 09:09 AM, Richard Earnshaw wrote:
> Valid pointers is more than just non-NULL.  In particular, it implies
> that is safe to dereference the addressed byte in a source operand even
> when the length parameter is zero.

I just reread C99 7.1.4 clause 1 and 7.21.2 clause 2, and I don't see 
that implication.  For example, the following program appears to be 
strictly conforming:

    #include <string.h>

    char src[1];
    char dst[1];

    int
    main (void)
    {
      memcpy (dst, src + 1, 0);
      return 0;
    }

Here, src + 1 is a valid pointer even though one cannot safely 
dereference it.  So it appears to be reasonable to check that memcpy 
doesn't dereference the source when the size is zero.