Re: [PATCH] Handle SIGSEGV in gdb selftests

[Simon Marchi <simark@simark.ca>]

On 12/26/22 03:02, tdevries via Gdb-patches wrote:
> On 2022-12-16 16:11, Tom Tromey via Gdb-patches wrote:
>>>>>>> "Tom" == Tom de Vries <tdevries@suse.de> writes:
>>
>> Tom> On 12/15/22 22:14, Tom Tromey via Gdb-patches wrote:
>>>> The gdb.gdb self-tests were timing out for me.  Looking into it, the
>>>> problem is that the version of the Boehm GC that is used by Guile on
>>>> my machine causes a SEGV during stack probing.  This unexpected stop
>>>> confuses the tests and causes repeated timeouts.
>>>>
>>
>> Tom> FWIW, that's https://sourceware.org/bugzilla/show_bug.cgi?id=29325 .
>>
>> Thanks, I updated the commit message.
> 
> I ran into this again, tried out the patch and checked that it fixes the problem.
> 
> LGTM.
> 
> Thanks,
> - Tom

Hi both Toms,

I still see the issue on Ubuntu 22.04, when testing with the
native-extended-gdbserver board:

...
Thread 1 "xgdb" received signal SIGSEGV, Segmentation fault.
0x00007ffff6d828f2 in GC_find_limit_with_bound () from /usr/lib/x86_64-linux-gnu/libgc.so.1
(gdb) FAIL: gdb.gdb/selftest.exp: xgdb is at prompt

The modified code looks like this:


        set test "xgdb is at prompt"
        gdb_test_multiple "continue" $test {
            -i "$inferior_spawn_id"
            -re "received signal SIGSEGV.* in GC_.*$gdb_prompt" {
                # Some versions of the GC used by Guile cause a SEGV
                # during stack probing.  Ignore this and carry on.
                send_gdb "continue\n"
                exp_continue
            }
            -re "$banner" {
                pass $test
            }
        }

Shouldn't the SIGSEGV -re be before the `-i $inferior_spawn_id`?
Otherwise we expect the "received signal SIGSEGV" message to come from
the debugged GDB, when it's the top GDB that will print it (like when
debugging any other test program).

I think we don't see the problem when testing with native because
the top and bottom GDBs share the same spawn id.

Simon