[clang] [clang][sema] Fixed a crash when mixture of designated and non-designated initializers in union (PR #114424)

[Congcong Cai via cfe-commits]

https://github.com/HerrCai0907 created https://github.com/llvm/llvm-project/pull/114424

Fixed: #113855
When the first init element is invalid, StructuredList can be empty.
It cause illegal state if we still set initialized field.


>From 0e4dd975f2139243bebdffe53aa9fde39a734730 Mon Sep 17 00:00:00 2001
From: Congcong Cai <congcongcai0907 at 163.com>
Date: Fri, 1 Nov 2024 00:13:59 +0800
Subject: [PATCH] [clang][sema] Fixed a crash when mixture of designated and
 non-designated initializers in union

Fixed: #113855
When the first init element is invalid, StructuredList can be empty.
It cause illegal state if we still set initialized field.
---
 clang/docs/ReleaseNotes.rst     |  1 +
 clang/lib/Sema/SemaInit.cpp     |  9 ++++++---
 clang/test/SemaCXX/PR113855.cpp | 15 +++++++++++++++
 3 files changed, 22 insertions(+), 3 deletions(-)
 create mode 100644 clang/test/SemaCXX/PR113855.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 0a1d0fd85e7ae0..a3449b96c313e0 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -404,6 +404,7 @@ Bug Fixes to C++ Support
 - Fixed an assertion failure in debug mode, and potential crashes in release mode, when
   diagnosing a failed cast caused indirectly by a failed implicit conversion to the type of the constructor parameter.
 - Fixed an assertion failure by adjusting integral to boolean vector conversions (#GH108326)
+- Fixed a crash when mixture of designated and non-designated initializers in union. (#GH113855)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 4d11f2a43fcc6b..0158cac5eb7166 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -2251,6 +2251,10 @@ bool InitListChecker::CheckFlexibleArrayInit(const InitializedEntity &Entity,
   return FlexArrayDiag != diag::ext_flexible_array_init;
 }
 
+static bool isInitializedStructuredList(const InitListExpr *StructuredList) {
+  return StructuredList && StructuredList->getNumInits() == 1U;
+}
+
 void InitListChecker::CheckStructUnionTypes(
     const InitializedEntity &Entity, InitListExpr *IList, QualType DeclType,
     CXXRecordDecl::base_class_const_range Bases, RecordDecl::field_iterator Field,
@@ -2497,8 +2501,7 @@ void InitListChecker::CheckStructUnionTypes(
                         StructuredList, StructuredIndex);
     InitializedSomething = true;
     InitializedFields.insert(*Field);
-
-    if (RD->isUnion() && StructuredList) {
+    if (RD->isUnion() && isInitializedStructuredList(StructuredList)) {
       // Initialize the first field within the union.
       StructuredList->setInitializedFieldInUnion(*Field);
     }
@@ -2583,7 +2586,7 @@ void InitListChecker::CheckStructUnionTypes(
     CheckImplicitInitList(MemberEntity, IList, Field->getType(), Index,
                           StructuredList, StructuredIndex);
 
-  if (RD->isUnion() && StructuredList) {
+  if (RD->isUnion() && isInitializedStructuredList(StructuredList)) {
     // Initialize the first field within the union.
     StructuredList->setInitializedFieldInUnion(*Field);
   }
diff --git a/clang/test/SemaCXX/PR113855.cpp b/clang/test/SemaCXX/PR113855.cpp
new file mode 100644
index 00000000000000..fb2a448eca0452
--- /dev/null
+++ b/clang/test/SemaCXX/PR113855.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct S {};
+
+union U {
+   S x;
+   float y;
+};
+
+void f() {
+   new U{0,.y=1};
+  // expected-warning at -1 {{mixture of designated and non-designated initializers in the same initializer list is a C99 extension}}
+  // expected-note at -2 {{first non-designated initializer is here}}
+  // expected-error at -3 {{initializer for aggregate with no elements requires explicit braces}}
+}