[lldb][DWARFASTParserClang][ObjC] Remove workaround for old ObjC DWARF #120218
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With all the recent versions of Clang that I tested, ObjC forward declarations like ``` @Class ForwardObjcClass; ``` don't emit the kind of DWARF that this workaround was put in place for. Also, zero-sized structures are valid in C (and thus Objective-C), so this workaround makes things confusing to reason about when mixing the two languages. This workaround has been in place for at least a decade, and given that recent compilers to produce this anymore, we think it's a good time to remove it.
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@llvm/pr-subscribers-lldb Author: Michael Buch (Michael137) ChangesWith all the recent versions of Clang that I tested, ObjC forward declarations like don't emit the kind of DWARF that this workaround was put in place for. Also, zero-sized structures are valid in C (and thus Objective-C), so this workaround makes things confusing to reason about when mixing the two languages. This workaround has been in place for at least a decade, and given that recent compilers don't produce this anymore, we think it's a good time to remove it. Full diff: https://github.com/llvm/llvm-project/pull/120218.diff 1 Files Affected:
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index 58f7b805abe2fd..3f49ad25710a9f 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -1657,20 +1657,6 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
ConstString unique_typename(attrs.name);
Declaration unique_decl(attrs.decl);
uint64_t byte_size = attrs.byte_size.value_or(0);
- if (attrs.byte_size && *attrs.byte_size == 0 && attrs.name &&
- !die.HasChildren() && cu_language == eLanguageTypeObjC) {
- // Work around an issue with clang at the moment where forward
- // declarations for objective C classes are emitted as:
- // DW_TAG_structure_type [2]
- // DW_AT_name( "ForwardObjcClass" )
- // DW_AT_byte_size( 0x00 )
- // DW_AT_decl_file( "..." )
- // DW_AT_decl_line( 1 )
- //
- // Note that there is no DW_AT_declaration and there are no children,
- // and the byte size is zero.
- attrs.is_forward_declaration = true;
- }
if (attrs.name) {
GetUniqueTypeNameAndDeclaration(die, cu_language, unique_typename,
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Michael137
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Dec 23, 2024
llvm#120218) With all the recent versions of Clang that I tested, ObjC forward declarations like ``` @Class ForwardObjcClass; ``` don't emit the kind of DWARF that this workaround was put in place for. Also, zero-sized structures are valid in C (and thus Objective-C), so this workaround makes things confusing to reason about when mixing the two languages. This workaround has been in place for at least a decade, and given that recent compilers don't produce this anymore, we think it's a good time to remove it. (cherry picked from commit 794cd81)
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With all the recent versions of Clang that I tested, ObjC forward declarations like
don't emit the kind of DWARF that this workaround was put in place for.
Also, zero-sized structures are valid in C (and thus Objective-C), so this workaround makes things confusing to reason about when mixing the two languages.
This workaround has been in place for at least a decade, and given that recent compilers don't produce this anymore, we think it's a good time to remove it.