[patch] Make "C++98 requires an accessible copy constructor" warning DefaultIgnore

[Richard Smith]

On Sat, Sep 6, 2014 at 5:31 PM, Nico Weber <thakis at chromium.org> wrote:

> On Sat, Sep 6, 2014 at 5:02 PM, Nico Weber <thakis at chromium.org> wrote:
>
>> On Sat, Sep 6, 2014 at 4:38 PM, Richard Smith <richard at metafoo.co.uk>
>> wrote:
>>
>>> -Wc++98-compat doesn't make sense here: that warning group is for
>>> warning on code that is valid in the current language but not in C++98.
>>>
>>
>> The same is true for warn_cxx98_compat_enumerator_list_comma (which is
>> in CXX98CompatPedantic) too though, right?
>>
>
That's not how the cxx98_compat warnings work. This is what we do there:

      if (!getLangOpts().C99 && !getLangOpts().CPlusPlus11)
        Diag(CommaLoc, getLangOpts().CPlusPlus ?
               diag::ext_enumerator_list_comma_cxx :
               diag::ext_enumerator_list_comma_c)
          << FixItHint::CreateRemoval(CommaLoc);
      else if (getLangOpts().CPlusPlus11)
        Diag(CommaLoc, diag::warn_cxx98_compat_enumerator_list_comma)
          << FixItHint::CreateRemoval(CommaLoc);

Note that we never produce a -Wc++98-compat warning in C++98 mode. And we
do a similar thing for this warning, but it's a little more complex because
we can't go through the motions of creating the temporary in C++11 mode,
since that might trigger template instantiations we're not allowed to
perform etc.

…anyhoo, here's a version that just makes this warning an Extension.
>

You should move over ext_rvalue_to_reference_temp_copy_no_viable too. It
doesn't make sense to downgrade only one of these two to an extension
(either we ignore the temporary copy as an extension or we don't; we
shouldn't be halfway between).


> I didn't move CXX98CompatBindToTemporaryCopy to CXX98CompatPedanticbecause
> that seems like an unrelated change,
>

It isn't: -Wc++98-compat-pedantic is supposed to warn on things that would
warned about in -pedantic C++98 mode. Since you're moving this warning from
ExtWarn to Extension, that means the corresponding -Wc++98-compat warning
should move to -Wc++98-compat-pedantic.

and because it contradicts the comment above CXX98CompatPedantic:
>
> // Warnings for C++11 features which are Extensions in C++98 mode.
>

You're making the C++11 "ignore the temporary copy when binding a reference
to a temporary of the same type" feature an Extension in C++98 mode, so
-Wc++98-compat-bind-to-temporary-copy belongs in the
-Wc++98-compat-pedantic group in C++11 mode. I don't see a contradiction
with the comment, but maybe we could clarify it somehow?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20140906/e37b646a/attachment.html>