Re: [patch] python(+solib error): save/restore error state

[Doug Evans <dje@google.com>]

On Fri, Oct 8, 2010 at 1:08 PM, Doug Evans <dje@google.com> wrote:
> On Fri, Oct 8, 2010 at 12:11 PM, Jan Kratochvil
> <jan.kratochvil@redhat.com> wrote:
>> @@ -768,6 +782,13 @@ source_python_script_for_objfile (struct objfile *objfile,
>>      clear the error indicator.  */
>>   PyRun_SimpleFile (stream, file);
>>
>> +  if (PyErr_Occurred ())
>> +    {
>> +      gdbpy_print_stack ();
>> +      error (_("Error reading python script %s for object file %s"), file,
>> +            objfile->name);
>> +    }
>> +
>>   do_cleanups (cleanups);
>>   gdbpy_current_objfile = NULL;
>>  }
>
> Hi.  Most of the patch seems great, but it raises a question that I
> think needs to be answered.
>
> The comment above this code says:
>
>  /* Note: If an exception occurs python will print the traceback and
>     clear the error indicator.  */
>
> ISTM that either this comment is wrong or the above patch is wrong, or
> some combination thereof.
>
> Also, if there is a problem here, then presumably source_python_script
> has the same problem, but I don't see it addressed in this patch.
>
> Plus if PyRun_SimpleFile can leave an outstanding error, we should
> research whether PyRun_SimpleString has the same problem.  I see
> python.c checks the result of PyRun_SimpleString and calls
> gdbpy_print_stack if there's an error.  Except that the python docs
> say there is no way to get the error.
>
> ref: http://docs.python.org/c-api/veryhigh.html?highlight=pyrun_simplestring#PyRun_SimpleString
>
> The docs for PyRun_SimpleFile suggest the same, there is no way to get
> the error.
>
> So, am I misreading the python docs or do we need the above patch?
> (and then if not, do we need the calls to gdbpy_print_stack after the
> calls to PyRun_SimpleString? Some experiments are in order - off to do
> some ...
>

Better yet, "use the source Luke ..." 1/2 :-).
Looking at the sources for PyRun_SimpleFile, I see PyErr_Print being
called before -1 is returned.
Similarly for PyRun_SimpleString.

Am I missing something?