[clang] [clang][CodeGen] Fix crash in CGDebugInfo on incomplete record type (#156352) (PR #197928)

[via cfe-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-debuginfo

Author: Vitor Ramos (VitorRamos)

<details>
<summary>Changes</summary>

Fix a crash when generating debug info for a template class that is
still being defined when its forward declaration is needed.

getTypeIdentifier() called getVTableLinkage() on a record that was only
"being defined" (not yet complete), which triggered premature
ASTRecordLayout computation and cached a layout with zero fields. Later,
CollectRecordFields used the stale cached layout and crashed on an
out-of-bounds field offset access.

Replace getDefinition() with isCompleteDefinition() to correctly skip
records whose definition is not yet complete.

Fixes #<!-- -->156352

---
Full diff: https://github.com/llvm/llvm-project/pull/197928.diff


2 Files Affected:

- (modified) clang/lib/CodeGen/CGDebugInfo.cpp (+1-1) 
- (added) clang/test/CodeGenCXX/debug-info-template-incomplete-record.cpp (+83) 


``````````diff
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 578d09f7971d6..71a21f19fbd5b 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -1290,7 +1290,7 @@ static SmallString<256> getTypeIdentifier(const TagType *Ty, CodeGenModule &CGM,
   if (!needsTypeIdentifier(TD, CGM, TheCU))
     return Identifier;
   if (const auto *RD = dyn_cast<CXXRecordDecl>(TD))
-    if (RD->getDefinition())
+    if (RD->isCompleteDefinition())
       if (RD->isDynamicClass() &&
           CGM.getVTableLinkage(RD) == llvm::GlobalValue::ExternalLinkage)
         return Identifier;
diff --git a/clang/test/CodeGenCXX/debug-info-template-incomplete-record.cpp b/clang/test/CodeGenCXX/debug-info-template-incomplete-record.cpp
new file mode 100644
index 0000000000000..f81433d53d296
--- /dev/null
+++ b/clang/test/CodeGenCXX/debug-info-template-incomplete-record.cpp
@@ -0,0 +1,83 @@
+// RUN: %clang_cc1 -std=c++20 -debug-info-kind=standalone -fvisibility=hidden \
+// RUN:   -O2 -triple x86_64-linux-gnu -emit-llvm %s -o - | FileCheck %s
+//
+// Verify that we don't crash when generating debug info for a template class
+// that is still being defined when its forward declaration is needed. The bug
+// was that getTypeIdentifier() called getVTableLinkage() on a record that was
+// only "being defined" (not yet complete), which triggered premature
+// ASTRecordLayout computation and cached a layout with zero fields. Later,
+// CollectRecordFields used the stale cached layout and crashed on an
+// out-of-bounds field offset access.
+
+class a;
+template<class>
+class b;
+class c
+{
+public:
+   using d = a;
+};
+template<class>
+class f;
+template<class e>
+class h
+{
+   using j = typename e::j;
+   j k();
+};
+class l;
+class m
+{
+   using i = f<l>;
+   i n();
+};
+template<class>
+class f
+{
+public:
+   using e = l;
+   using o = e;
+   using d = b<e>;
+   d *p;
+};
+class L;
+class q
+{
+public:
+   using j = L;
+};
+class r
+{
+   ~r();
+   h<q> s;
+};
+r::~r() = default;
+class l
+{
+public:
+   using j = m;
+   using g = c;
+};
+class J
+{
+   h<l> t;
+};
+class a
+{
+public:
+   virtual ~a();
+};
+template<class e>
+class b : e::g::d
+{
+   using u = typename f<e>::o;
+   int v;
+};
+class L : J
+{
+};
+extern template class b<l>;
+
+// Just verify we produce debug info for b<l> with its field v.
+// CHECK: !DICompositeType(tag: DW_TAG_class_type, name: "b<l>"
+// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "v"

``````````

</details>


https://github.com/llvm/llvm-project/pull/197928