Fix crash when trying to pack-expand a GNU statement expression.

We could in principle support such pack expansion, using techniques similar to
what we do for pack expansion of lambdas, but it's not clear it's worthwhile.
For now at least, cleanly reject these cases rather than crashing.

llvm-svn: 324160

1 files changed, 12 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index d81837dad50..7aa0e317df0 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -314,8 +314,18 @@ Sema::DiagnoseUnexpandedParameterPacks(SourceLocation Loc,
   // later.
   SmallVector<UnexpandedParameterPack, 4> LambdaParamPackReferences;
   for (unsigned N = FunctionScopes.size(); N; --N) {
-    if (sema::LambdaScopeInfo *LSI =
-          dyn_cast<sema::LambdaScopeInfo>(FunctionScopes[N-1])) {
+    sema::FunctionScopeInfo *Func = FunctionScopes[N-1];
+    // We do not permit pack expansion that would duplicate a statement
+    // expression, not even within a lambda.
+    // FIXME: We could probably support this for statement expressions that do
+    // not contain labels, and for pack expansions that expand both the stmt
+    // expr and the enclosing lambda.
+    if (std::any_of(
+            Func->CompoundScopes.begin(), Func->CompoundScopes.end(),
+            [](sema::CompoundScopeInfo &CSI) { return CSI.IsStmtExpr; }))
+      break;
+
+    if (auto *LSI = dyn_cast<sema::LambdaScopeInfo>(Func)) {
       if (N == FunctionScopes.size()) {
         for (auto &Param : Unexpanded) {
           auto *PD = dyn_cast_or_null<ParmVarDecl>(