Re: [PATCH] Defer breakpoint reset when cloning progspace for fork child

[Pedro Alves <palves at redhat dot com>]

On 04/07/2018 06:52 PM, Simon Marchi wrote:

>> This issue happens only with position-independent executables.  Adding
>> the main objfile for the new inferior (the fork child) causes GDB to try
>> to reset the breakpoints.  However, that new objfile has not been
>> relocated yet.  So the breakpoint on "break_here" resolves to an
>> unrelocated address, from which we are trying to read/write to set a
>> breakpoint.  Passing SYMFILE_DEFER_BP_RESET avoids that problem.  The
>> executable is relocated just after, in the follow_fork_inferior
>> function.
>>

>> The buildbot seems happy with this patch.  I don't think it's necessary
>> to add a new test.  Just changing this made many tests go from FAIL to
>> PASS on my machine, where gcc produces PIE executables by default.  If
>> anything, I think we would need to add a board file that produces
>> position-independent executables, so that we can run all the tests with
>> PIE, even on machines where that is not the default.
> 
> I pushed this patch.

Thanks for the fix.

I'm not sure I agree with no test, though.  I think a simple test
that tries both pie and not-pie would be useful, because
defaults vary depending on distro/system and they change over
time -- having a smoke test like the one described above covering both
pie and non-pie ensures no developer or testing environment where pie
might be relevant ever misses the problem in the future.

Thanks,
Pedro Alves