Re: [PATCH] Introduce gdb_interact in testsuite

Simon Marchi
2015-01-22T20:52:47Z

On 15-01-20 08:42 PM, Doug Evans wrote:
> On Thu, Jan 15, 2015 at 8:40 AM, Simon Marchi <simon.marchi@ericsson.com> wrote:
>>
>> gdb_interact is a small utility that we have found quite useful to debug
>> test cases.
>>
>> Putting gdb_interact in a test suspends it and allows to interact with
>> gdb to inspect whatever you want. You can then type ">>>" to resume the
>> test execution. Of course, this is only for gdb devs. It wouldn't make
>> sense to leave a gdb_interact permanently in a test case.
>>
>> When starting the interaction with the user, the script prints this
>> banner:
>>
>> +------------------------------------------+
>> | Script interrupted, you can now interact |
>> | with by gdb. Type >>> to continue. |
>> +------------------------------------------+
>>
>> Notes:
>> * When gdb is launched, the gdb_spawn_id variable (lib/gdb.exp) is
>> assigned -1. Given the name, I would expect it to contain the gdb
>> expect spawn id, which is needed for interact. I changed all places
>> that set gdb_spawn_id to -1 to set it to the actual gdb spawn id
>> instead.
>>
>> * When entering the "interact" mode, the last (gdb) prompt is already
>> eaten by expect, so it doesn't show up on the terminal. Subsequent
>> prompts do appear though. We tried to print "(gdb)" just before the
>> interact to replace it. However, it could be misleading if you are
>> debugging an MI test case, it makes you think that you are typing in a
>> CLI prompt, when in reality it's MI. In the end I decided that since
>> the feature is for developers who know what they're doing and that one
>> is normally consciously using gdb_interact, the script doesn't need
>> to babysit the user.
>>
>> * There are probably some quirks depending on where in the script
>> gdb_interact appears (e.g. it could interfere with following
>> commands and make them fail), but it works for most cases. Quirks can
>> always be fixed later.
>>
>> The idea and original implementation was contributed by Anders
>> Granlund, a colleague of mine. Thanks to him.
>>
>> gdb/testsuite/ChangeLog:
>>
>> * gdb.base/statistics.exp: Assign spawn id to gdb_spawn_id.
>> * gdb.base/valgrind-db-attach.exp: Same.
>> * gdb.base/valgrind-infcall.exp: Same.
>> * lib/mi-support.exp (default_mi_gdb_start): Same.
>> * lib/prompt.exp (default_prompt_gdb_start): Same.
>> * lib/gdb.exp (default_gdb_spawn): Same.
>> (gdb_interact): New.
>
> [Apologies for the resend.]
>
> I'm not sure why we're assigning -1 instead of a usable value,
> but I can't find anything to suggest assigning a real id will
> cause problems.
>
> Plus given how trivial gdb_interact is, the patch is fine by me.
>
> Another way such things are debugged is by first running tests
> with TRANSCRIPT=y, and then massaging the transcript.N files
> afterwards. I'm all for adding more ways of debugging tests.
> Thanks!

Thanks, pushed.