Re: [PATCH] gdb/testsuite: Run test when software watchpoints are used

[Simon Marchi <simark@simark.ca>]

On 2018-07-06 09:59, Andrew Burgess wrote:
> I think you give me too much credit!
> 
> What happened was I had a target without h/w watchpoints, I ran the
> GDB testsuite and had a set of passes and fails.  After some
> investigation I realised that I'd neglected to mark the target as not
> supporting h/w watchpoints in the board file.
> 
> Once I'd added the no h/w watchpoint flag in the board file I reran
> the tests, and mostly things looked better.  Failures, or unresolved
> tests had become unsupported.
> 
> However.... in watchpoint-reuse-slot.exp a number of tests that used
> to pass had gone away, so I went looking at the test script.
> 
> What I saw was that though the test declared a need for h/w
> watchpoints, the test would run perfectly fine without them.
> 
> You'll notice that with my change if the board file says that h/w
> watchpoints are supported then we still look for the full "Hardware
> watchpoint" pattern in the output, that is, my change does not mean
> that if GDB broke and h/w watchpoints changed to s/w watchpoints (when
> they shouldn't) the test would pass.  I think that after my change all
> targets that previously ran this test are just as well tested as they
> ever were.
> 
> But, we have additional s/w watchpoint testing for targets that don't
> support h/w watchpoints.  Is this testing anything that's not covered
> elsewhere?  Honestly, I don't know.  There probably is a lot of test
> duplication, but I can't guarantee that there's nothing unique in
> here.
> 
> I guess my question is, what's the harm from broadening the test in
> this way?  If I've missed something and this change could mean a bug
> can now slip into GDB then absolutely, this is not acceptable.  But, I
> can't see how (yet)...

Indeed, I see no harm in running more tests, at worst it's useless.  
Maybe
it will find some bug in the software watchpoint code.

I was thinking that we might as well run it with software watchpoints 
even
with targets that support hardware watchpoints.  We could run 
unconditionally
with "set can-use-hw-watchpoints 0" and run it with "1" on targets that
support hw watchpoints.

Simon