[all-commits] [llvm/llvm-project] 7bd92f: [AST] Pick last tentative definition as the acting...

[Benson Chu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7bd92f5911dc7ec54200d37552d364f87ad03dfb
      https://github.com/llvm/llvm-project/commit/7bd92f5911dc7ec54200d37552d364f87ad03dfb
  Author: Benson Chu <bensonchu457 at gmail.com>
  Date:   2021-08-26 (Thu, 26 Aug 2021)

  Changed paths:
    M clang/lib/AST/Decl.cpp
    A clang/test/CodeGen/attr-tentative-definition.c

  Log Message:
  -----------
  [AST] Pick last tentative definition as the acting definition

Clang currently picks the second tentative definition when
VarDecl::getActingDefinition is called.

This can lead to attributes being dropped if they are attached to
tentative definitions that appear after the second one. This is
because VarDecl::getActingDefinition loops through VarDecl::redecls
assuming that the last tentative definition is the last element in the
iterator. However, it is the second element that would be the last
tentative definition.

This changeset modifies getActingDefinition to iterate through the
declaration chain in reverse, so that it can immediately return when
it encounters a tentative definition.

Originally the unit test for this changeset did not have a -triple
flag for the clang invocation, leading to this test being broken on
MacOS, since Mach-O does not support the section attribute.

Differential Revision: https://reviews.llvm.org/D99732