[sema] enhance error handling for compound stmt body in StmtExpr

clang/docs/ReleaseNotes.rst

@@ -443,6 +443,7 @@ Bug Fixes in This Version
 - The warning emitted for an unsupported register variable type now points to
   the unsupported type instead of the ``register`` keyword (#GH109776).
 - Fixed a crash when emit ctor for global variant with flexible array init  (#GH113187).
+- Fixed a crash when GNU statement expression contains invalid statement (#GH113468).
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Parse/ParseStmt.cpp

@@ -1243,6 +1243,7 @@ StmtResult Parser::ParseCompoundStatementBody(bool isStmtExpr) {
       ParsedStmtContext::Compound |
       (isStmtExpr ? ParsedStmtContext::InStmtExpr : ParsedStmtContext());
 
+  bool LastIsError = false;
   while (!tryParseMisplacedModuleImport() && Tok.isNot(tok::r_brace) &&
          Tok.isNot(tok::eof)) {
     if (Tok.is(tok::annot_pragma_unused)) {
@@ -1299,7 +1300,15 @@ StmtResult Parser::ParseCompoundStatementBody(bool isStmtExpr) {
 
     if (R.isUsable())
       Stmts.push_back(R.get());
+    LastIsError = R.isInvalid();
   }
+  // StmtExpr needs to do copy initialization for last statement.
+  // If last statement is invalid, the last statement in `Stmts` will be
+  // incorrect. Then the whole compound statement should also be marked as
+  // invalid to prevent subsequent errors.
+  if (isStmtExpr && LastIsError && !Stmts.empty())
+    return StmtError();
+
   // Warn the user that using option `-ffp-eval-method=source` on a
   // 32-bit target and feature `sse` disabled, or using
   // `pragma clang fp eval_method=source` and feature `sse` disabled, is not

clang/test/SemaCXX/gh113468.cpp

@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify %s
+
+constexpr int expr() {
+  if (({
+        int f;
+        f = 0;
+        if (f)
+          break; // expected-error {{'break' statement not in loop or switch statement}}
+      }))
+    return 2;
+  return 1;
+}