Re: c/4967: GCC should warn about obvious violations of restrict

[Andreas Jaeger <aj at suse dot de>]

"Joseph S. Myers" <jsm28@cam.ac.uk> writes:

> On Thu, 29 Nov 2001, Andreas Jaeger wrote:
>
>> whether a call is defined or not.  A call sprintf_restrict (buf, buf)
>> would only be undefined when the function writes to both pointers but
>> this cannot be detected at the call side for e.g. library
>> functions:-(.
>
> Only when it writes to the same object via one pointer as it accesses by
> the other, indeed.  Adding 25 to the second pointer, then copying 25 bytes
> from the first to the second, or something more complicated where each
> byte is only accessed via one of the pointers, would still be OK.
>
> You could always work out some way to annotate function declarations with
> information about how much is read or written from each argument and
> whether aliasing is OK (note that the restrict qualifiers in declarations
> not part of the definition are still irrelevant and are effectively
> ignored (6.7.5.3#15), but you could define them to be relevant in

that's much more involved then the simple solution I had in mind -
which is not ok :-(

> interpreting such an attribute).  I'd like to get -Wformat-security to
> warn about sprintf into fixed-length buffers that might be too short for
> the format, and similar such possible security holes.

I'm closing this bug report now, since what I orignally intented is
not possible.

Thanks,
Andreas
-- 
 Andreas Jaeger
  SuSE Labs aj@suse.de
   private aj@arthur.inka.de
    http://www.suse.de/~aj