[PATCH] D129531: [clang][C++20] P0960R3: Allow initializing aggregates from a parenthesized list of values

[Alan Zhao via Phabricator via cfe-commits]

ayzhao added a comment.

Status update:

While investigating @cor3ntin's comment about refactoring `VisitInitListExpr` and `VisitCXXParenListInitExpr` as they share common code, I discovered that flexible array members would cause this patch to explode. Specifically, the following code:

  struct S {
      int b;
      int a[];
  };
  
  S s2(1, {1, 2});

was causing this assertion <https://github.com/llvm/llvm-project/blob/3f18f7c0072b642f5fe88d2fb7bb8ccf69a6c6f5/clang/lib/CodeGen/CGExprAgg.cpp#L480> to fail.

I took a look at GCC, and it turns out that GCC doesn't allow flexible array members at all in paren list initialization of aggregates, even in contexts where the corresponding designated initializer expression succeeds: https://godbolt.org/z/E73433erb

For now, I updated this implementation to follow GCC's behavior and disallow flexible array members, as IIRC in C++ they are a GCC extension and we should therefore follow GCC behavior. However, I am open to other thoughts.


Repository:
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