[Lldb-commits] [clang] [lldb] [clang][AST] Added assert to prevent infinite recursion in computing layout (PR #154123)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (tgs-sc)

<details>
<summary>Changes</summary>

    [lldb][DWARFASTParserClang] Added a check for the specialization existence

    While debugging an application with incorrect dwarf information, where
    DW_TAG_template_value_parameter was lost, I found that lldb does not
    check that the corresponding specialization exists. As a result, at the
    stage when ASTImporter works, the type is completed in such a way that
    it inherits from itself. And during the calculation of layout, an
    infinite recursion occurs. To catch this error, I added a corresponding check
    at the stage of restoring the type from dwarf information. I also added a
    trivial assert in clang to check that the class does not inherit from itself.

---
Full diff: https://github.com/llvm/llvm-project/pull/154123.diff


2 Files Affected:

- (modified) clang/lib/AST/RecordLayoutBuilder.cpp (+2) 
- (modified) lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp (+16) 


``````````diff
diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 6d819031cbef4..93571543f1c7d 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -187,6 +187,8 @@ void EmptySubobjectMap::ComputeEmptySubobjectSizes() {
   // Check the bases.
   for (const CXXBaseSpecifier &Base : Class->bases()) {
     const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
+    // Assert to prevent infinite recursion.
+    assert(BaseDecl != Class && "Class cannot inherit from itself.");
 
     CharUnits EmptySize;
     const ASTRecordLayout &Layout = Context.getASTRecordLayout(BaseDecl);
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index c76d67b47b336..6643751cd237a 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -1873,6 +1873,22 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
     clang_type =
         m_ast.CreateClassTemplateSpecializationType(class_specialization_decl);
 
+    // Try to find an existing specialization with these template arguments and
+    // template parameter list.
+    void *InsertPos = nullptr;
+    if (!class_template_decl->findSpecialization(template_param_infos.GetArgs(),
+                                                 InsertPos))
+      // Add this specialization to the class template.
+      class_template_decl->AddSpecialization(class_specialization_decl,
+                                             InsertPos);
+    else {
+      dwarf->GetObjectFile()->GetModule()->ReportError(
+          "SymbolFileDWARF({0:p}) - Specialization for "
+          "clang::ClassTemplateDecl({1:p}) already exists.",
+          static_cast<void *>(this), static_cast<void *>(class_template_decl));
+      return TypeSP();
+    }
+
     m_ast.SetMetadata(class_template_decl, metadata);
     m_ast.SetMetadata(class_specialization_decl, metadata);
   }

``````````

</details>


https://github.com/llvm/llvm-project/pull/154123