[PATCH] D79512: [DebugInfo][CodeView] Fix lowering of UDT

[Alexandre Ganea via Phabricator via llvm-commits]

aganea created this revision.
aganea added reviewers: rnk, akhuang.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.
aganea marked an inline comment as done.
aganea added inline comments.
aganea edited the summary of this revision.


================
Comment at: llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp:363
+  // looping in emitDebugInfoForUDTs.
+  TypeLoweringScope S(*this);
+  SmallVector<StringRef, 5> QualifiedNameComponents;
----------------
The actual change is this line.


It seems my previous changes uncovered an issue:

See build log here: http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/41191/steps/check-llvm%20msan/logs/stdio
And here: http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/builds/17119/steps/check-llvm%20asan/logs/stdio

What happens is that `emitDebugInfoForGlobal` calls `getFullyQualifiedName`, which in turn calls `CodeViewDebug::collectParentScopeNames` and then, `DeferredCompleteTypes.push_back(Ty);`

This leaves deferred types in the vector, but they are only 'applied' later, inadvertently by `emitDebugInfoForUDTs` while calling `getCompleteTypeIndex` which ends up destroying a `TypeLoweringScope` which applies the deferred types, which in turn creates new UDT, which resizes the vector being iterated in the first place in `emitDebugInfoForUDTs`.

I've added an extra `TypeLoweringScope` in `getFullyQualifiedName()` below, which should only fire if there are no other `TypeLoweringScope` in the stack (which is the case for `emitDebugInfoForGlobal`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79512

Files:
  llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp


Index: llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -343,18 +343,6 @@
   return FullyQualifiedName;
 }
 
-std::string CodeViewDebug::getFullyQualifiedName(const DIScope *Scope,
-                                                 StringRef Name) {
-  SmallVector<StringRef, 5> QualifiedNameComponents;
-  collectParentScopeNames(Scope, QualifiedNameComponents);
-  return formatNestedName(QualifiedNameComponents, Name);
-}
-
-std::string CodeViewDebug::getFullyQualifiedName(const DIScope *Ty) {
-  const DIScope *Scope = Ty->getScope();
-  return getFullyQualifiedName(Scope, getPrettyScopeName(Ty));
-}
-
 struct CodeViewDebug::TypeLoweringScope {
   TypeLoweringScope(CodeViewDebug &CVD) : CVD(CVD) { ++CVD.TypeEmissionLevel; }
   ~TypeLoweringScope() {
@@ -367,6 +355,22 @@
   CodeViewDebug &CVD;
 };
 
+std::string CodeViewDebug::getFullyQualifiedName(const DIScope *Scope,
+                                                 StringRef Name) {
+  // Ensure types in the scope chain are emitted as soon as possible.
+  // This can create otherwise a situation where S_UDTs are emitted while
+  // looping in emitDebugInfoForUDTs.
+  TypeLoweringScope S(*this);
+  SmallVector<StringRef, 5> QualifiedNameComponents;
+  collectParentScopeNames(Scope, QualifiedNameComponents);
+  return formatNestedName(QualifiedNameComponents, Name);
+}
+
+std::string CodeViewDebug::getFullyQualifiedName(const DIScope *Ty) {
+  const DIScope *Scope = Ty->getScope();
+  return getFullyQualifiedName(Scope, getPrettyScopeName(Ty));
+}
+
 TypeIndex CodeViewDebug::getScopeIndex(const DIScope *Scope) {
   // No scope means global scope and that uses the zero index.
   if (!Scope || isa<DIFile>(Scope))


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