[clang] [clang] Fix crash when compiling error with invalid decl (PR #77893)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Qizhi Hu (jcsxky)

<details>
<summary>Changes</summary>

`APValue::LValueBase::LValueBase` constructs `ValueDecl` with its canonicalDecl, even though it's invalid. And when obtain its type, it also check all redecls and ignore checking if it's valid. This will cause crash in invalid code. This patch fixes this issue by checking its validation and skip invalid decls.
Fix [issue](https://github.com/llvm/llvm-project/issues/69468)

---
Full diff: https://github.com/llvm/llvm-project/pull/77893.diff


2 Files Affected:

- (modified) clang/lib/AST/APValue.cpp (+6-2) 
- (added) clang/test/AST/invalid-decl-no-crash.cpp (+12) 


``````````diff
diff --git a/clang/lib/AST/APValue.cpp b/clang/lib/AST/APValue.cpp
index 4eae308ef5b34c..b1fd93b23f38cc 100644
--- a/clang/lib/AST/APValue.cpp
+++ b/clang/lib/AST/APValue.cpp
@@ -40,7 +40,11 @@ static_assert(
     "Type is insufficiently aligned");
 
 APValue::LValueBase::LValueBase(const ValueDecl *P, unsigned I, unsigned V)
-    : Ptr(P ? cast<ValueDecl>(P->getCanonicalDecl()) : nullptr), Local{I, V} {}
+    : Ptr(P ? cast<ValueDecl>(P->getCanonicalDecl()->isInvalidDecl()
+                                  ? P
+                                  : P->getCanonicalDecl())
+            : nullptr),
+      Local{I, V} {}
 APValue::LValueBase::LValueBase(const Expr *P, unsigned I, unsigned V)
     : Ptr(P), Local{I, V} {}
 
@@ -73,7 +77,7 @@ QualType APValue::LValueBase::getType() const {
     for (auto *Redecl = cast<ValueDecl>(D->getMostRecentDecl()); Redecl;
          Redecl = cast_or_null<ValueDecl>(Redecl->getPreviousDecl())) {
       QualType T = Redecl->getType();
-      if (!T->isIncompleteArrayType())
+      if (!T->isIncompleteArrayType() && !Redecl->isInvalidDecl())
         return T;
     }
     return D->getType();
diff --git a/clang/test/AST/invalid-decl-no-crash.cpp b/clang/test/AST/invalid-decl-no-crash.cpp
new file mode 100644
index 00000000000000..2b35ef702ae553
--- /dev/null
+++ b/clang/test/AST/invalid-decl-no-crash.cpp
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fsyntax-only %s -verify
+
+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) {
+  a[j] = b[j];
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/77893