[PATCH] D28148: [Sema] Suppress warnings for C's zero initializer

John McCall via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Thu Dec 29 18:46:00 PST 2016

rjmccall added a comment.

In https://reviews.llvm.org/D28148#632541, @Quuxplusone wrote:

> Re the language option: In https://reviews.llvm.org/D27163, @rsmith wrote:
> > Perhaps some catch-all "I want defined behavior for things that C defines even though I'm compiling in C++" flag would make sense here?
> It didn't happen then, but I'd like to re-raise the idea. There's probably plenty of code (e.g. Apple kernel drivers, judging from @rjmccall's comments on https://reviews.llvm.org/D27163) that's written in the common subset of C and C++ but compiled as C++. It's unfortunate that that workflow keeps getting "broken" by aggressive diagnostics (in this case) and aggressive optimizations (in that case). I'd like if Clang provided a way for the user to explicitly opt-in and say "Some or all of this code is C compiled as C++; please respect that."
> (IOW, it looks as if this patch proposes to fix the noisy diagnostic for every language //except for// C-sometimes-compiled-as-C++, and as a sometime writer of C-sometimes-compiled-as-C++ myself, that irks me. Apologies if I've misconstrued the patch.)

C++, for all its problems, does fix some things about C.  I don't think it makes all that much sense to support a general "this is C being compiled as C++" mode, especially for diagnostics where (generally) compiling things as C++ ends up applying a more sensible language rule than C provides.  We tend to have a lot more diagnostics that are basically pointing out flaws in C that C++ fixes than the other way around.


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