comex added inline comments.
================
Comment at: test/SemaCXX/auto-type-from-cxx.cpp:14
@@ +13,3 @@
+ auto _ = [](__auto_type f) {}; // expected-error {{'__auto_type' not allowed
in lambda parameter}}
+ __auto_type g = 2;
+ struct BitField { int field:2; };
----------------
thakis wrote:
> comex wrote:
> > thakis wrote:
> > > Shouldn't this say "warning: __auto_type is a gnu extension" (since this
> > > uses -std=c++14, not -std=gnu++14)?
> > Hmm... when I added `ext_auto_type` to the .td, I didn't notice the
> > difference between Extension and ExtWarn. Since the patch currently uses
> > Extension, it won't warn by default, but will with `-pedantic`, `-Wgnu`, or
> > `-Wgnu-auto-type`. The C test uses `-pedantic` so it gets the warning.
> >
> > Is there an explicit policy on which extensions should be ExtWarn? Looking
> > at the rest of that file, ExtWarns seem to be mostly either (a)
> > standardized extensions (which will warn if `-std` is too early) and (b)
> > 'extensions' that are more like "Clang will accept your buggy code" than
> > features. Most GNU extensions are just Extension, so I think it makes
> > sense to do the same for `__auto_type`.
> >
> > I could update the C++ test to add `-pedantic`, but arguably it makes more
> > sense to test the fact that the warning is not emitted by default.
> I'm not sure either. `typeof` warns with -std=c++14 but not with
> -std=gnu++14. From a user perspective, this makes sense to me: I want to
> write standard c++ and I want the compiler to help me with that, but I don't
> want to get all the pedantic warnings that -pedantic entails. For example,
> consider using clang-cl to build Windows code, and wanting MSVC to be able to
> build said Windows code too. (This can of course go wrong with standard C++
> too, but in that case I'm running into MSVC bugs which will eventually be
> fixed.) So if it's possible to match how typeof works, I think that'd be
> good. If it's not possible, this wouldn't be the only GNU extension allowed
> in -std=c++14 mode though, so it's not a big thing.
As far as I can tell, `typeof` doesn't warn at all. In standard mode it's an
*error* because `typeof` is treated as a normal identifier (so that code that
uses it as such doesn't break), but if you use the reserved-namespace keyword
`__typeof`, there is no warning even with `-Weverything`.
http://reviews.llvm.org/D12686
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