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

[Florian Weimer]

On 09/23/2014 02:57 PM, Richard Earnshaw wrote:
> On 23/09/14 13:41, Florian Weimer wrote:
>> 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.
>
> I don't think such a pointer forms a valid argument for a library
> function though.  See my previous reply to Paul.

They are a fairly common occurrence with the [first, last) iterator 
ranges in C++.  It's common to compute a pointer/length pair {first, 
last - first} and pass that to C functions, including C library functions.

This pattern is already incorrect in important corner cases (e.g., 
iterators derived from empty vectors), but do we really have to make the 
situation even worse?

-- 
Florian Weimer / Red Hat Product Security