[ was: Re: [PATCH][gdb/testsuite] Work around skip_prologue problems in
gdb.threads/process-dies-while-detaching.exp ]

On 11/2/21 6:13 PM, Kevin Buettner wrote:
> On Tue, 2 Nov 2021 12:38:26 +0100
> Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> wrote:
> 
>> On 10/29/21 9:24 PM, Tom de Vries via Gdb-patches wrote:
>>> Hi,
>>>
>>> On powerpc64le-linux, I run into:
>>> ...
>>> [Inferior 1 (process 5156) exited normally]^M
>>> (gdb) FAIL: gdb.threads/process-dies-while-detaching.exp: single-process: \
>>>   detach: detach: continue to breakpoint: _exit (the program exited)
>>> ...
>>>
>>> What happens is the following:
>>> - a breakpoint is set on _exit,
>>> - a continue is issued
>>> - the continue is supposed to hit the breakpoint, but instead
>>>   the program exits.
>>>
>>> I traced this down to the breakpoint on _exit being set too far from function
>>> entry.  This is caused by the skip_prologue function (in rs6000-tdep.c)
>>> optimistically ignoring insns it doesn't recognize.  In particular, it walks
>>> past the system call instruction "sc" which initiates the actual exit.
>>>
>>> While this needs fixing,  
>>
>> Filed here: https://sourceware.org/bugzilla/show_bug.cgi?id=28527 .
>>
>> Submitted patch here:
>> https://sourceware.org/pipermail/gdb-patches/2021-November/183016.html .
>>
>> Thanks,
>> - Tom
>>
>>> we don't want to be testing this behaviour in this
>>> test-case.
> 
> Since you've fixed the problem in skip_prologue(), I'd prefer that this
> testsuite patch not go in.

One possible objection would be that otherwise we no longer excercise
the problem, so here's a test-case for that.

Any comments?

Thanks,
- Tom