[PATCH] D123649: Allow flexible array initialization in C++.

[Eli Friedman via Phabricator via cfe-commits]

efriedma added inline comments.


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Comment at: clang/test/SemaCXX/constant-expression-cxx11.cpp:2388
+  // evaluation. Make sure we emit a sane error message, for now.
+  constexpr A c = {1, 2, 3}; // expected-warning {{flexible array initialization is a GNU extension}}
+  static_assert(c.arr[0] == 1, ""); // expected-error {{constant expression}} expected-note {{array member without known bound}}
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erichkeane wrote:
> I would expect this to be an error, not the static-assert.  The constexpr variable means 'initializable as a constant expression'.  
> 
> I'm guessing the problem is ACTUALLY that we support constexpr init, but not the operator[].  I think I'd like to have us have the initialization fail here, since it isn't otherwise usable.
I think we end up computing the initializer "correctly", but have no way to actually access the elements in constant evaluation.  Seems to come out of CGExprConstant lowering okay, but I guess we don't really need that to work at the moment; we fall back to the old CGExprConstant direct lowering code.

I'll add a bailout to constant evaluation.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D123649/new/

https://reviews.llvm.org/D123649