[clang] [Clang][AST] Fix crash in APValue::LValueBase::getType when we have invalid decl (PR #75130)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Shafik Yaghmour (shafik)

<details>
<summary>Changes</summary>

In some cases when calling APValue::LValueBase::getType() when we have a ValueDecl in some cases we don't handle invalid decls. We iterating over redeclarations we reset the current decl to the current most recent decl and we check the next redeclaration to ensure it is not invalid.

Fixes: https://github.com/llvm/llvm-project/issues/69468

---
Full diff: https://github.com/llvm/llvm-project/pull/75130.diff


2 Files Affected:

- (modified) clang/lib/AST/APValue.cpp (+3-1) 
- (added) clang/test/AST/gh69468.cpp (+14) 


``````````diff
diff --git a/clang/lib/AST/APValue.cpp b/clang/lib/AST/APValue.cpp
index 4eae308ef5b34..2ccd83a1d4823 100644
--- a/clang/lib/AST/APValue.cpp
+++ b/clang/lib/AST/APValue.cpp
@@ -70,11 +70,13 @@ QualType APValue::LValueBase::getType() const {
     // constexpr int *p = &arr[1]; // valid?
     //
     // For now, we take the most complete type we can find.
-    for (auto *Redecl = cast<ValueDecl>(D->getMostRecentDecl()); Redecl;
+    for (auto *Redecl = cast<ValueDecl>(D->getMostRecentDecl());
+         Redecl && !Redecl->isInvalidDecl();
          Redecl = cast_or_null<ValueDecl>(Redecl->getPreviousDecl())) {
       QualType T = Redecl->getType();
       if (!T->isIncompleteArrayType())
         return T;
+      D = Redecl;
     }
     return D->getType();
   }
diff --git a/clang/test/AST/gh69468.cpp b/clang/test/AST/gh69468.cpp
new file mode 100644
index 0000000000000..8c93fa5e828ac
--- /dev/null
+++ b/clang/test/AST/gh69468.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -verify %s
+
+
+a[i] = b[i]; // expected-error {{use of undeclared identifier 'i'}} \
+             // expected-error {{a type specifier is required for all declarations}} \
+	     // expected-error {{use of undeclared identifier 'b'}} \
+	     // expected-error {{use of undeclared identifier 'i'}}
+extern char b[];
+extern char a[];
+
+void foo(int j) {
+  // This used to crash here
+  a[j] = b[j];
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/75130