[PATCH 3/8] d2d1/tests: Avoid out-of-bounds access when comparing segments

[Stefan Brüns]

On Dienstag, 11. Januar 2022 16:47:14 CET you wrote:
> On Tue, 11 Jan 2022 at 08:55, Stefan Brüns <stefan.bruens at rwth-aachen.de> 
wrote:
> > On Freitag, 7. Januar 2022 18:10:05 CET you wrote:
> > > On Fri, 7 Jan 2022 at 09:00, Stefan Brüns <stefan.bruens at rwth-aachen.de>
> > 
> > wrote:
> > > > In case real and expected segment count differ, don't compare the
> > > > segment type/position for extra segments.
> > > 
> > > Unless it's e.g. a huge help when debugging failures, I'm not sure we
> > > care; if the segment counts don't match the test is going to fail, one
> > > way or another.
> > 
> > This is an invalid memory access (though read-only). This should never be
> > done, even in tests.
> 
> That's not the position the Wine project has historically taken on
> this kind of thing, at least when it comes to the tests. The basic
> idea is that the test isn't supposed to fail, so when it does, we
> don't particularly care about any follow-up damage. (Provided that's
> limited to the test process.) I.e., think of ok() much like assert().

The follow-up damage is not only to the process, but most importantly to the 
person trying to debug  the issue.

In case the segments do not match (which is the more likely case, as it is 
just random data for the extraneous segments), it print totally bogus 
coordinates. This is confusing at best, printing a totally wrong message 
("mismatching segments") and random coordinates.

In case the segments do match (possible, as the allocated memory may reuse 
memory of an previous test, and coordinates of sequential tests are often 
similar), no coordinates are printed.


For someone very familiar with the code, this might be expected. For anybody 
else debugging becomes harder. I have wasted half an hour getting what was 
actually going on, and this change would have saved me the time.

Kind regards,

Stefan

-- 
Stefan Brüns  /  Bergstraße 21  /  52062 Aachen
phone: +49 241 53809034     mobile: +49 151 50412019
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