commit 6eb9b9e593b133fe766a31442df4ad4a110e0fa2
author Richard Smith <richard-llvm@metafoo.co.uk> Sat Feb 03 00:44:57 2018 +0000
committer Richard Smith <richard-llvm@metafoo.co.uk> Sat Feb 03 00:44:57 2018 +0000
tree 575525f3e11be8f9de2a00f1dcfa3a5db1a0af64
parent 35eb6c856a8f18f238fbad2752f7cc85049d6e95

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

clang/lib/Sema/Sema.cpp

diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index e07f609..45fd2d3 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -1393,8 +1393,8 @@
     delete Scope;
 }
 
-void Sema::PushCompoundScope() {
-  getCurFunction()->CompoundScopes.push_back(CompoundScopeInfo());
+void Sema::PushCompoundScope(bool IsStmtExpr) {
+  getCurFunction()->CompoundScopes.push_back(CompoundScopeInfo(IsStmtExpr));
 }
 
 void Sema::PopCompoundScope() {

clang/lib/Sema/SemaStmt.cpp

diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 1ebc367..9390703 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -337,8 +337,8 @@
   DiagRuntimeBehavior(Loc, nullptr, PDiag(DiagID) << R1 << R2);
 }
 
-void Sema::ActOnStartOfCompoundStmt() {
-  PushCompoundScope();
+void Sema::ActOnStartOfCompoundStmt(bool IsStmtExpr) {
+  PushCompoundScope(IsStmtExpr);
 }
 
 void Sema::ActOnFinishOfCompoundStmt() {

clang/lib/Sema/SemaTemplateVariadic.cpp

diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index d81837d..7aa0e31 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -314,8 +314,18 @@
   // 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>(