[cfe-dev] Does `#pragma GCC diagnostic warning` intentionally win over -Werror?

[Nico Weber via cfe-dev]

On Thu, Jan 24, 2019 at 11:12 AM James Y Knight <jyknight at google.com> wrote:

> I don't think we should have such a flag. The explicit intent of '#pragma
> gcc diagnostic warning' is to allow downgrading an error to a warning,
> while still allowing it to be emitted.
>
> Perhaps a new value for pragma diagnostic which emits an upgradeable
> warning would be reasonable.
>

The use case here is that we don't allow non-error diagnostics in chrome.
Some subproject used `#pragma GCC diagnostic warning` because they wanted
to configure warning flags in cc files instead of in build files for some
reason. They didn't expect this to trigger a warning instead of an error. A
new pragma would meet that use case, but I don't want source code to be
able to opt out of -Werror. In my experience, once it's known that such an
option exist, someone will use it. So we do need some kind of "_all_
warnings are errors" toggle.


>
> On Thu, Jan 24, 2019 at 9:56 AM Nico Weber via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> Re "intentional?", it matches gcc which explicitly documents on
>> https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html that the
>> pragma wins over -Werror.
>>
>> Does anyone know if there's a flag that says "I want all warnings to be
>> errors, not just most of them"?
>>
>> If there isn't one yet, what would be a good UI for that?
>>
>> On Wed, Jan 23, 2019 at 11:11 PM Nico Weber <thakis at chromium.org> wrote:
>>
>>> Consider:
>>>
>>> $ cat test.cc
>>> #pragma GCC diagnostic warning "-Wsign-compare"
>>>
>>> bool f(int a, unsigned b) {
>>>   return a != b;
>>> }
>>> $ out/gn/bin/clang -c test.cc -Werror
>>> test.cc:4:12: warning: comparison of integers of different signs: 'int'
>>> and 'unsigned int' [-Wsign-compare]
>>>   return a != b;
>>>          ~ ^  ~
>>> 1 warning generated.
>>>
>>>
>>> I found it surprising that this is emitted as a warning, not as an
>>> error. If this is intentional, is there some other way to say "I want my
>>> compiler warnings to always be errors"?
>>>
>>> Thanks,
>>> Nico
>>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20190124/9165ea0d/attachment.html>