[cfe-commits] [Patch][Review] __has_feature(__feature__)

[Richard Smith]

Thanks! I've committed this (with 80 column fixes / minor copy edits) as
r151445.

On Sat, Feb 25, 2012 at 12:36 AM, Jonathan Sauer <jonathan.sauer at gmx.de>wrote:

> Hello,
>
> >> following the discussion in cfe-dev[*], I decided to put my money where
> my mouth is and have attached a patch
> >> that makes it possible to use __has_feature(__feature__) in place of
> __has_feature(feature) to protect the
> >> feature name in case the user defines a macro with the same name.
> >>
> >> I modeled the patch after the similar handling of __attribute__ names.
> >
> > This patch looks great to me, please commit!
>
> As I have not commit access, I would kindly ask someone who has to do it
> for me.
>
> I updated the patch to include Jean-Daniel's suggestion to handle
> __has_extension the same way. I also
> modified the code slightly to make the normalization of the name work
> without invoking undefined
> behaviour in case the string is shorter than 4 characters: Before, it
> depended on the assumption that an
> unsigned integer underflow would result in a very large integer, which was
> then ignored as it was larger
> than the string size. As this also was the case when normalizing the
> attribute name, I modified that
> code as well.
>
> I don't think that a feature "has_feature_supports_double_underscore" or
> similar is necessary. Simply
> choose an arbitrary extension that is always supported in clang and check
> for the feature with and
> without underscores:
>
>  #if __has_extension(c_alignas) && !__has_extension(__c_alignas__)
>  #  message Double underscores in extension names are not supported
>  #else
>  #  message Double underscores in extension names are supported
>  #endif
>
> If you disagree, just tell me and I'll add it.
>
>
> I have attached the new patch.
>
>
> Jonathan
>
>
>
>
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>
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