make check (testing): how to re-test just 1 failed test src file?

[U.Mutlu]

Jeff Law wrote on 07/19/2018 07:55 PM:
> On 07/19/2018 11:39 AM, U.Mutlu wrote:
>> After doing a
>>    make -j5 -k check-gcc-c RUNTESTFLAGS="-v -v"
>> and creating the report, one gets such results, for example:
> [ ... ]
> You have to know which .exp file runs your test.    Given that...
>
> make RUNTESTFLAGS="whatever.exp"
>
> Will run the subset of tests for that .exp file.
>
>
> Many .exp files can run individual tests.  So something like this will
> often run a test on a single .c file:
>
>
> make RUNTESTFLAGS=execute.exp=930513-1.c

Thx, this now works (the exp file is dg-torture.exp), but the adventure 
continues... :-)

The next question is: how can I debug that in gdb?

runtest --help says there's a --debug switch and -D1.
But this invokes the tcl debugger (have zero experience with that tcl-script 
debugger).

What would you experienced people suggest to do to find out
why this specific test is failing on x86_64 host=target ?
I find it a little bit mysterious why it fails, and would like to know more 
about the exact reason.

Thx