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

[Florian Weimer]

On 09/22/2014 06:09 PM, Richard Earnshaw wrote:
>> These tests are not testing null pointers, they are testing that when
>> given a zero length the functions actually read/write zero bytes.
>> Whether the specification demands that behaviour is arguable but I
>> believe that it is the most sane behaviour.

> 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.

Valid pointers can also point one element past the end of an array of 
objects.  Such pointers can occur naturally during the final iteration 
of buffer-processing loops.  I don't think it is reasonable to expect 
that programmers write special code (or at least early loop exits) to 
deal with this corner case.  This has to work, and if the C standard 
does not guarantee it does, it needs fixing.

> Thus testing that no bytes are read would be incorrect.

I disagree, per the above.

-- 
Florian Weimer / Red Hat Product Security