[PATCH] D156565: Diagnose use of VLAs in C++ by default

[James Y Knight via Phabricator via cfe-commits]

jyknight added inline comments.


================
Comment at: clang/lib/Sema/SemaType.cpp:2617
+  } else if (getLangOpts().CPlusPlus) {
+    if (getLangOpts().CPlusPlus11 && IsStaticAssertLike(ArraySize, Context))
+      VLADiag = getLangOpts().GNUMode
----------------
aaron.ballman wrote:
> jyknight wrote:
> > Not sure whether to actually care, since C++98 is so old now, but, having `-Wno-vla-extension-static-assert` work in C++98 mode seems like it'd be quite useful, exactly because the usage cannot trivially be replaced by a static_assert. So it's a bit unfortunate that we don't distinguish it there.
> > 
> > Perhaps we should emit the same diagnostics in both 98/11, but with slightly different text in 98?
> That's effectively what we're doing here, right?
> 
> C++98 is told "variable length arrays (in C++) are a Clang extension" and in C++11 they're told "variable length arrays (in C++) are a Clang extension; did you mean to use 'static_assert'?"
> 
> Or am I misunderstanding you?
In this patch, in C++98 mode, we diagnose everything under the flag -Wvla-extension, and never under the flag -Wvla-extension-static-assert. My point was that we ought to diagnose static-assert-like-VLAs under the -Wvla-extension-static-assert flag even in C++98 mode.


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  https://reviews.llvm.org/D156565/new/

https://reviews.llvm.org/D156565