[clang] [Clang][Sema] fix crash of attribute transform (PR #78088)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Qizhi Hu (jcsxky)

<details>
<summary>Changes</summary>

Try to fix [issue](https://github.com/llvm/llvm-project/issues/73619)

1. During transforming `FunctionProtoType`, if `ThisContext,` is `nullptr` and `CurrentContext` is `ClassTemplateSpecializationDecl`, Constructor of `CXXThisScopeRAII` and `Sema::getCurrentThisType` won't set `CXXThisTypeOverride` of Sema. This will lead to building `this` in `RebuildCXXThisExpr` with a invalid type and cause crash.
2. During transforming attribute type, if `modifiedType` of attribute type is changed, `EquivalentType` will be transformed. If `EquivalentType` is `FunctionProtoType`, its `ParamVarDecl` will not be copyed(but parameter num does) and will not be instanced in `TransformFunctionTypeParams` since `ParamVarDecl` is `nullptr`. This will lead to crash in `findInstantiationOf`.

This patch tries to fix these issue above.

1. If `CurrentContext` is `ClassTemplateSpecializationDecl`, Use it.
2. Use `EquivalentTypeLoc` instead of `EquivalentType` since it has parameter info. But, if use current `TypeLocBuilder`, it will crash in `TypeLocBuilder::push` since `LastType` is mismatch. Use an auxiliary `TypeLocBuilder` instead and get transformed `EquivalentType`.

---
Full diff: https://github.com/llvm/llvm-project/pull/78088.diff


3 Files Affected:

- (modified) clang/include/clang/AST/TypeLoc.h (+4) 
- (modified) clang/lib/Sema/TreeTransform.h (+8-3) 
- (added) clang/test/Sema/attr-lifetimebound-no-crash.cpp (+15) 


``````````diff
diff --git a/clang/include/clang/AST/TypeLoc.h b/clang/include/clang/AST/TypeLoc.h
index 471deb14aba51f..04780fdeae3bc1 100644
--- a/clang/include/clang/AST/TypeLoc.h
+++ b/clang/include/clang/AST/TypeLoc.h
@@ -884,6 +884,10 @@ class AttributedTypeLoc : public ConcreteTypeLoc<UnqualTypeLoc,
     return getInnerTypeLoc();
   }
 
+  TypeLoc getEquivalentTypeLoc() const {
+    return TypeLoc(getTypePtr()->getEquivalentType(), getNonLocalData());
+  }
+
   /// The type attribute.
   const Attr *getAttr() const {
     return getLocalData()->TypeAttr;
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 1a1bc87d2b3203..be5ba2000de197 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -6124,7 +6124,11 @@ QualType TreeTransform<Derived>::TransformFunctionProtoType(
       //   "pointer to cv-qualifier-seq X" between the optional cv-qualifer-seq
       //   and the end of the function-definition, member-declarator, or
       //   declarator.
-      Sema::CXXThisScopeRAII ThisScope(SemaRef, ThisContext, ThisTypeQuals);
+      auto *RD =
+          dyn_cast_or_null<CXXRecordDecl>(SemaRef.getCurLexicalContext());
+      Sema::CXXThisScopeRAII ThisScope(
+          SemaRef, ThisContext == nullptr && nullptr != RD ? RD : ThisContext,
+          ThisTypeQuals);
 
       ResultType = getDerived().TransformType(TLB, TL.getReturnLoc());
       if (ResultType.isNull())
@@ -7083,8 +7087,9 @@ QualType TreeTransform<Derived>::TransformAttributedType(
       modifiedType != oldType->getModifiedType()) {
     // TODO: this is really lame; we should really be rebuilding the
     // equivalent type from first principles.
-    QualType equivalentType
-      = getDerived().TransformType(oldType->getEquivalentType());
+    TypeLocBuilder AuxiliaryTLB;
+    QualType equivalentType =
+        getDerived().TransformType(AuxiliaryTLB, TL.getEquivalentTypeLoc());
     if (equivalentType.isNull())
       return QualType();
 
diff --git a/clang/test/Sema/attr-lifetimebound-no-crash.cpp b/clang/test/Sema/attr-lifetimebound-no-crash.cpp
new file mode 100644
index 00000000000000..32e015bab02918
--- /dev/null
+++ b/clang/test/Sema/attr-lifetimebound-no-crash.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 %s -verify -fsyntax-only
+
+template<typename T>
+struct Bar {
+    int* data;
+
+    auto operator[](const int index) const [[clang::lifetimebound]] -> decltype(data[index]) {
+        return data[index];
+    }
+};
+
+int main() {
+    Bar<int> b;
+    (void)b[2];
+}
\ No newline at end of file

``````````

</details>


https://github.com/llvm/llvm-project/pull/78088