[PATCH] D83972: Modify ImportDefiniton for ObjCInterfaceDecl so that we always the ImportDeclContext one we start the definition

[Shafik Yaghmour via Phabricator via cfe-commits]

shafik created this revision.
shafik added reviewers: teemperor, martong.
Herald added a subscriber: rnkovacs.

Once we start the definition of an `ObjCInterfaceDecl` we won't attempt to `ImportDeclContext` later on. Unlike `RecordDecl` case which uses `DefinitionCompleter` to force `completeDefinition` we don't seem to have a similar mechanism for `ObjCInterfaceDecl`.

This fix was needed due to a bug we see in LLDB expression parsing where an initial expression cause an `ObjCInterfaceDecl` to be defined and subsequent expressions during import do not call `ImportDeclContext` and we can end up in a situation where ivars are imported out of order and not all ivars are imported e.g.

  (lldb) expr chb1->hb->field2
  ObjCInterfaceDecl 0x7f9457495fe0 <<invalid sloc>> <invalid sloc> <undeserialized declarations> HasBitfield1
  |-super ObjCInterface 0x7f9457495e78 'NSObject'
  `-ObjCIvarDecl 0x7f945749d478 <<invalid sloc>> <invalid sloc> field2 'unsigned int' public
    `-IntegerLiteral 0x7f945749d458 <<invalid sloc>> 'int' 1

We have `field2` which is the second ivar but we are missing `field1`.

In this particular case `ASTContext::lookupFieldBitOffset(...)` assumes we have all ivars and they are in order to obtain the index of the ivar and we break this assumption. This leads eventually to bad IRGen since it has the wrong field offset.


https://reviews.llvm.org/D83972

Files:
  clang/lib/AST/ASTImporter.cpp
  lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
  lldb/test/API/lang/objc/bitfield_ivars/Makefile
  lldb/test/API/lang/objc/bitfield_ivars/TestBitfieldIvars.py
  lldb/test/API/lang/objc/bitfield_ivars/main.m

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