[PATCH] D106994: [modules] Fix miscompilation when using two RecordDecl definitions with the same name.

[Volodymyr Sapsai via Phabricator via cfe-commits]

vsapsai created this revision.
vsapsai added reviewers: rsmith, bruno, teemperor.
Herald added a subscriber: ributzka.
vsapsai requested review of this revision.
Herald added a project: clang.

When deserializing a RecordDecl we don't enforce that redeclaration
chain contains only a single definition. So if the canonical decl is not
a definition itself, `RecordType::getDecl` can return different objects
before and after an include. It means we can build CGRecordLayout for
one RecordDecl with its set of FieldDecl but try to use it with
FieldDecl belonging to a different RecordDecl. With assertions enabled
it results in

> Assertion failed: (FieldInfo.count(FD) && "Invalid field for record!"),
> function getLLVMFieldNo, file llvm-project/clang/lib/CodeGen/CGRecordLayout.h, line 199.

and with assertions disabled a bunch of fields are treated as their
memory is located at offset 0.

Fix by keeping the first encountered RecordDecl definition and marking
the subsequent ones as non-definitions. Also need to merge FieldDecl
properly, so that `getPrimaryMergedDecl` works correctly and during name
lookup we don't treat fields from same-name RecordDecl as ambiguous.

rdar://80184238


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D106994

Files:
  clang/include/clang/Serialization/ASTReader.h
  clang/lib/Serialization/ASTReaderDecl.cpp
  clang/test/Modules/Inputs/merge-record-definition/RecordDef.framework/Headers/RecordDef.h
  clang/test/Modules/Inputs/merge-record-definition/RecordDef.framework/Modules/module.modulemap
  clang/test/Modules/Inputs/merge-record-definition/RecordDefCopy.framework/Headers/RecordDefCopy.h
  clang/test/Modules/Inputs/merge-record-definition/RecordDefCopy.framework/Modules/module.modulemap
  clang/test/Modules/Inputs/merge-record-definition/RecordDefHidden.framework/Headers/Hidden.h
  clang/test/Modules/Inputs/merge-record-definition/RecordDefHidden.framework/Headers/Visible.h
  clang/test/Modules/Inputs/merge-record-definition/RecordDefHidden.framework/Modules/module.modulemap
  clang/test/Modules/Inputs/merge-record-definition/RecordDefIncluder.framework/Headers/RecordDefIncluder.h
  clang/test/Modules/Inputs/merge-record-definition/RecordDefIncluder.framework/Modules/module.modulemap
  clang/test/Modules/merge-record-definition-nonmodular.m
  clang/test/Modules/merge-record-definition-visibility.m
  clang/test/Modules/merge-record-definition.m

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