[Bug python/31391] Incorrect FinishBreakpoint test

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31391

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #1)
> (In reply to Tom Tromey from comment #0)
> > py-finishbreakpoint.exp does this:
> > 
> >     gdb_test "python print (finishbp_default.hit_count)" "1.*" "check
> > finishBP on default frame has been hit"
> > 
> > It is trying to check the hit count of this breakpoint.
> > However, the actual output is:
> > 
> > python print (finishbp_default.hit_count)
> > Traceback (most recent call last):
> >   File "<string>", line 1, in <module>
> > RuntimeError: Breakpoint 3 is invalid.
> > Error while executing Python code.
> > 
> > 
> > ... which matches by mistake.
> > This came up in a patch series I'm working on.
> > 
> > I plan to kfail this but not close this bug; I think
> > this probably is a real problem of some sort.
> 
> I think this may be the behaviour specified here (
> https://sourceware.org/gdb/current/onlinedocs/gdb.html/Breakpoints-In-Python.
> html ):
> ...
> The optional temporary argument makes the breakpoint a temporary breakpoint.
> Temporary breakpoints are deleted after they have been hit. Any further
> access to the Python breakpoint after it has been hit will result in a
> runtime error (as that breakpoint has now been automatically deleted).
> ...
> 
> So AFAIU, this happens:
> - finish breakpoints 3 and 4 are set at the same location
> - a continue hits both finish breakpoints
> - the hit_count is not available in either breakpoint, as per the doc,
> because
>   both temporary breakpoints have been deleted.
> - the return_value is available in both finish breakpoints, because it
> doesn't
>   rely on accessing the underlying python breakpoint
> 
> I think the test-case can be updated to accept the current behaviour, or we
> can even remove the hit_count test.

I'll write a patch to this effect.

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