[PATCH] D143533: [clang] Allow gnu::aligned attribute to work with templated type alias declarations

[Leonard Chan via Phabricator via cfe-commits]

leonardchan created this revision.
leonardchan added reviewers: rsmith, rnk, echristo.
leonardchan added a project: clang.
Herald added a subscriber: jeroen.dobbelaere.
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Prior to this, the following would fail:

  template <typename T>
  using NaturallyAligned [[gnu::aligned(sizeof(T))]] = T;
  
  struct S { char x[2]; };
  using AlignedS = NaturallyAligned<S>;
  static_assert(alignof(AlignedS) == 2);  // alignof(AlignedS) == 1

This is because clang ignores attributes on type aliases when evaluating type info and instead resolves to alignment of the replacement type `T`.

This patch attempts to check if the associated type declaration is an alias that contains an attribute and return whatever the value is indicated by the alignment expression.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D143533

Files:
  clang/lib/AST/ASTContext.cpp
  clang/test/SemaTemplate/type-alias-aligned.cpp

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