[DebugInfo] Produce debuginfo for nested types when the outer type is [[clang::standalone_debug]] #146175
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… [[clang::standalone_debug]]. Without this, it's impossible to get debuginfo for a nested type that is unused (or that clang mistakenly believes is unused due to e.g. deficiencies in -debug-info-kind=limited), even by marking the "unused" nested type itself with [[clang::standalone_debug]]. This makes writing pretty-printers and similar things difficult. The [[clang::standalone_debug]] attribute is not propagated to the nested type. But after applying [[clang::standalone_debug]] to the outer type to ensure the nested type appears in the debuginfo at all, a developer can also additionally apply the attribute to the nested type if desired.
llvmbot added clang 
| @llvm/pr-subscribers-clang @llvm/pr-subscribers-debuginfo Author: Kyle Huey (khuey) ChangesWithout this, it's impossible to get debuginfo for a nested type that is unused (or that clang mistakenly believes is unused due to e.g. deficiencies in -debug-info-kind=limited), even by marking the "unused" nested type itself with [[clang::standalone_debug]]. This makes writing pretty-printers and similar things difficult. The [[clang::standalone_debug]] attribute is not propagated to the nested type. But after applying [[clang::standalone_debug]] to the outer type to ensure the nested type appears in the debuginfo at all, a developer can also additionally apply the attribute to the nested type if desired. Full diff: https://github.com/llvm/llvm-project/pull/146175.diff 2 Files Affected:
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp index 7ab0e2fdaa731..d28bbcd9d9835 100644 --- a/clang/lib/CodeGen/CGDebugInfo.cpp +++ b/clang/lib/CodeGen/CGDebugInfo.cpp @@ -2075,12 +2075,13 @@ void CGDebugInfo::CollectRecordFields( // Bump field number for next field. ++fieldNo; - } else if (CGM.getCodeGenOpts().EmitCodeView) { + } else if (CGM.getCodeGenOpts().EmitCodeView || + record->hasAttr<StandaloneDebugAttr>()) { // Debug info for nested types is included in the member list only for - // CodeView. + // CodeView and types with the standalone_debug attribute. if (const auto *nestedType = dyn_cast<TypeDecl>(I)) { // MSVC doesn't generate nested type for anonymous struct/union. - if (isa<RecordDecl>(I) && + if (CGM.getCodeGenOpts().EmitCodeView && isa<RecordDecl>(I) && cast<RecordDecl>(I)->isAnonymousStructOrUnion()) continue; if (!nestedType->isImplicit() && diff --git a/clang/test/CodeGenCXX/standalone-debug-attribute-limited.cpp b/clang/test/CodeGenCXX/standalone-debug-attribute-limited.cpp new file mode 100644 index 0000000000000..43ec35db18c7d --- /dev/null +++ b/clang/test/CodeGenCXX/standalone-debug-attribute-limited.cpp @@ -0,0 +1,29 @@ +// RUN: %clang_cc1 -DSETATTR=0 -triple x86_64-unknown-linux-gnu -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=DEBUG +// RUN: %clang_cc1 -DSETATTR=1 -triple x86_64-unknown-linux-gnu -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=WITHATTR +// Use -debug-info-kind=limited because an unused type will never have a used ctor. + +#if SETATTR +#define STANDALONEDEBUGATTR __attribute__((standalone_debug)) +#else +#define STANDALONEDEBUGATTR +#endif + +struct STANDALONEDEBUGATTR TypeWithNested { + struct Unused1 { + }; + struct STANDALONEDEBUGATTR Unused2 { + }; + + int value = 0; +}; +void f(TypeWithNested s) {} +// DEBUG: !DICompositeType(tag: DW_TAG_structure_type, name: "TypeWithNested" +// DEBUG-NOT: !DICompositeType(tag: DW_TAG_structure_type, name: "Unused1" +// DEBUG-NOT: !DICompositeType(tag: DW_TAG_structure_type, name: "Unused2" +// WITHATTR: !DICompositeType(tag: DW_TAG_structure_type, name: "TypeWithNested" +// WITHATTR: !DICompositeType(tag: DW_TAG_structure_type, name: "Unused1" +// The STANDALONEDEBUGATTR isn't propagated to the nested type by default, so +// it should still be a forward declaration. +// WITHATTR-SAME: DIFlagFwdDecl +// WITHATTR: !DICompositeType(tag: DW_TAG_structure_type, name: "Unused2" +// WITHATTR-NOT: DIFlagFwdDecl |
| @llvm/pr-subscribers-clang-codegen Author: Kyle Huey (khuey) ChangesWithout this, it's impossible to get debuginfo for a nested type that is unused (or that clang mistakenly believes is unused due to e.g. deficiencies in -debug-info-kind=limited), even by marking the "unused" nested type itself with [[clang::standalone_debug]]. This makes writing pretty-printers and similar things difficult. The [[clang::standalone_debug]] attribute is not propagated to the nested type. But after applying [[clang::standalone_debug]] to the outer type to ensure the nested type appears in the debuginfo at all, a developer can also additionally apply the attribute to the nested type if desired. Full diff: https://github.com/llvm/llvm-project/pull/146175.diff 2 Files Affected:
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp index 7ab0e2fdaa731..d28bbcd9d9835 100644 --- a/clang/lib/CodeGen/CGDebugInfo.cpp +++ b/clang/lib/CodeGen/CGDebugInfo.cpp @@ -2075,12 +2075,13 @@ void CGDebugInfo::CollectRecordFields( // Bump field number for next field. ++fieldNo; - } else if (CGM.getCodeGenOpts().EmitCodeView) { + } else if (CGM.getCodeGenOpts().EmitCodeView || + record->hasAttr<StandaloneDebugAttr>()) { // Debug info for nested types is included in the member list only for - // CodeView. + // CodeView and types with the standalone_debug attribute. if (const auto *nestedType = dyn_cast<TypeDecl>(I)) { // MSVC doesn't generate nested type for anonymous struct/union. - if (isa<RecordDecl>(I) && + if (CGM.getCodeGenOpts().EmitCodeView && isa<RecordDecl>(I) && cast<RecordDecl>(I)->isAnonymousStructOrUnion()) continue; if (!nestedType->isImplicit() && diff --git a/clang/test/CodeGenCXX/standalone-debug-attribute-limited.cpp b/clang/test/CodeGenCXX/standalone-debug-attribute-limited.cpp new file mode 100644 index 0000000000000..43ec35db18c7d --- /dev/null +++ b/clang/test/CodeGenCXX/standalone-debug-attribute-limited.cpp @@ -0,0 +1,29 @@ +// RUN: %clang_cc1 -DSETATTR=0 -triple x86_64-unknown-linux-gnu -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=DEBUG +// RUN: %clang_cc1 -DSETATTR=1 -triple x86_64-unknown-linux-gnu -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s --check-prefix=WITHATTR +// Use -debug-info-kind=limited because an unused type will never have a used ctor. + +#if SETATTR +#define STANDALONEDEBUGATTR __attribute__((standalone_debug)) +#else +#define STANDALONEDEBUGATTR +#endif + +struct STANDALONEDEBUGATTR TypeWithNested { + struct Unused1 { + }; + struct STANDALONEDEBUGATTR Unused2 { + }; + + int value = 0; +}; +void f(TypeWithNested s) {} +// DEBUG: !DICompositeType(tag: DW_TAG_structure_type, name: "TypeWithNested" +// DEBUG-NOT: !DICompositeType(tag: DW_TAG_structure_type, name: "Unused1" +// DEBUG-NOT: !DICompositeType(tag: DW_TAG_structure_type, name: "Unused2" +// WITHATTR: !DICompositeType(tag: DW_TAG_structure_type, name: "TypeWithNested" +// WITHATTR: !DICompositeType(tag: DW_TAG_structure_type, name: "Unused1" +// The STANDALONEDEBUGATTR isn't propagated to the nested type by default, so +// it should still be a forward declaration. +// WITHATTR-SAME: DIFlagFwdDecl +// WITHATTR: !DICompositeType(tag: DW_TAG_structure_type, name: "Unused2" +// WITHATTR-NOT: DIFlagFwdDecl |
| @dwblaikie could you take a look at this? |
| I don't think this is the right direction. standalone_debug shouldn't affect truly unused types - I don't think nested or unnested unused types should be treated the same in this regard (because they are treated the same in every other regard, I think) Got a particular example of the problem? Perhaps there's some other solutions we could consider |
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Without this, it's impossible to get debuginfo for a nested type that is unused (or that clang mistakenly believes is unused due to e.g. deficiencies in -debug-info-kind=limited), even by marking the "unused" nested type itself with [[clang::standalone_debug]]. This makes writing pretty-printers and similar things difficult.
The [[clang::standalone_debug]] attribute is not propagated to the nested type. But after applying [[clang::standalone_debug]] to the outer type to ensure the nested type appears in the debuginfo at all, a developer can also additionally apply the attribute to the nested type if desired.