thakis 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; };
----------------
comex wrote:
> 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`.
Ah, ok. That's ok as-is then. It'd be nice if there was something that warning
on GNU extensions, but that's independent of this patch :-)
http://reviews.llvm.org/D12686
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