[clang] [clang][ExprConst] Fix crash on uninitialized array subobject (PR #67817)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

<details>
<summary>Changes</summary>

https://reviews.llvm.org/D146358 was assuming that all subobjects have
their own name (`SubobjectDecl`), but it was not true for array
elements.

Fixes https://github.com/llvm/llvm-project/issues/67317


---
Full diff: https://github.com/llvm/llvm-project/pull/67817.diff


4 Files Affected:

- (modified) clang/include/clang/Basic/DiagnosticASTKinds.td (+1-1) 
- (modified) clang/lib/AST/ExprConstant.cpp (+9-4) 
- (modified) clang/lib/AST/Interp/Interp.cpp (+1-1) 
- (modified) clang/test/SemaCXX/eval-crashes.cpp (+7) 


``````````diff
diff --git a/clang/include/clang/Basic/DiagnosticASTKinds.td b/clang/include/clang/Basic/DiagnosticASTKinds.td
index d2656310e79c9b8..71dabac2d32402a 100644
--- a/clang/include/clang/Basic/DiagnosticASTKinds.td
+++ b/clang/include/clang/Basic/DiagnosticASTKinds.td
@@ -69,7 +69,7 @@ def note_consteval_address_accessible : Note<
   "%select{pointer|reference}0 to a consteval declaration "
   "is not a constant expression">;
 def note_constexpr_uninitialized : Note<
-  "subobject %0 is not initialized">;
+  "subobject %select{of type |}0%1 is not initialized">;
 def note_constexpr_uninitialized_base : Note<
   "constructor of base class %0 is not called">;
 def note_constexpr_static_local : Note<
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index f0d53d6ae18e804..acf4b33242c4a27 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -2411,10 +2411,15 @@ static bool CheckEvaluationResult(CheckEvaluationResultKind CERK,
                                   const FieldDecl *SubobjectDecl,
                                   CheckedTemporaries &CheckedTemps) {
   if (!Value.hasValue()) {
-    assert(SubobjectDecl && "SubobjectDecl shall be non-null");
-    Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized) << SubobjectDecl;
-    Info.Note(SubobjectDecl->getLocation(),
-              diag::note_constexpr_subobject_declared_here);
+    if (SubobjectDecl) {
+      Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized)
+          << true << SubobjectDecl;
+      Info.Note(SubobjectDecl->getLocation(),
+                diag::note_constexpr_subobject_declared_here);
+    } else {
+      // FIXME: We should add a test to check the output of this case.
+      Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized) << false << Type;
+    }
     return false;
   }
 
diff --git a/clang/lib/AST/Interp/Interp.cpp b/clang/lib/AST/Interp/Interp.cpp
index e1951574edb6288..0e7e9bac1c8079a 100644
--- a/clang/lib/AST/Interp/Interp.cpp
+++ b/clang/lib/AST/Interp/Interp.cpp
@@ -404,7 +404,7 @@ bool CheckPure(InterpState &S, CodePtr OpPC, const CXXMethodDecl *MD) {
 static void DiagnoseUninitializedSubobject(InterpState &S, const SourceInfo &SI,
                                            const FieldDecl *SubObjDecl) {
   assert(SubObjDecl && "Subobject declaration does not exist");
-  S.FFDiag(SI, diag::note_constexpr_uninitialized) << SubObjDecl;
+  S.FFDiag(SI, diag::note_constexpr_uninitialized) << true << SubObjDecl;
   S.Note(SubObjDecl->getLocation(),
          diag::note_constexpr_subobject_declared_here);
 }
diff --git a/clang/test/SemaCXX/eval-crashes.cpp b/clang/test/SemaCXX/eval-crashes.cpp
index 3e59ad31c559da8..ac04b113f99b7aa 100644
--- a/clang/test/SemaCXX/eval-crashes.cpp
+++ b/clang/test/SemaCXX/eval-crashes.cpp
@@ -54,3 +54,10 @@ namespace pr33140_10 {
   int a(const int &n = 0);
   bool b() { return a() == a(); }
 }
+
+namespace GH67317 {
+struct array {
+  int (&data)[2];
+  array() : data(*new int[1][2]) {}
+};
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/67817