Re: [PATCH] Eliminate -var-create error for optzd ptr to struct

[Pedro Alves <palves at redhat dot com>]

On 04/05/2016 07:50 PM, Don Breazeal wrote:
> Hi Yao,
> 
> On 4/5/2016 5:52 AM, Yao Qi wrote:
>> Don Breazeal <donb@codesourcery.com> writes:
> 
>>> +      CATCH (ex, RETURN_MASK_ERROR)
>>> +	{
>>> +	  /* If we get an error, assume the value is not optimized out.  */
>>> +	  return 0;
>>
>> Why don't we fall back to checking value->optimized_out below?  Some
>> bits/pieces of value are optimized out, but reading the rest of
>> bits/piece may trigger the memory error.  In this case, the value is
>> optimized out too.  We can do this...
>>
>>          TRY
>>          {
>>            value_fetch_lazy (value);
>>          }
>>          CATCH (ex, RETURN_MASK_ERROR)
>>          {
>>            /* Fall back to checking value->optimized_out.  */
>>          }
>>          END_CATCH
>>
>> What do you think?
> 
> Of course, that makes more sense, thanks.
> 
>> Note that, after this patch, value_optimized_out will no longer throw
>> exceptions, some TRY/CATCH in value_optimized_out's callers can be
>> removed, such as gdbscm_value_optimized_out_p and
>> valpy_get_is_optimized_out.  This can be done in a follow-up patch.
> 
> I've done a more thorough audit of the call sites for value_optimized_out
> than I did previously, and the only places where an enclosing TRY/CATCH can
> be removed are the two you name.  There is one other place where it is
> called inside a TRY/CATCH, but there are other functions that could throw
> errors called there as well.
> 
> I will create a follow-up patch.
> 
> I changed this patch as you suggest above, as well as changing
> RETURN_MASK_ERROR to RETURN_MASK_ALL.  The TRY/CATCH blocks that are
> going to be removed use RETURN_MASK_ALL, and I thought that this patch
> should maintain the same level of coverage.

Please don't.  A RETURN_MASK_ALL swallows Ctrl-C/QUIT, and that's almost
always a bug.  The cases you mention translate a QUIT to a python/scheme
exception, which is not the same as just swallowing the exception.

Thanks,
Pedro Alves