From b035cd7ea4d59e7e76412940351f693ec421e15e Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron@aaronballman.com>
Date: Thu, 5 Nov 2015 00:06:05 +0000
Subject: [PATCH] The control expression for a _Generic selection expression
 should have its type decayed and qualifiers stripped when determining which
 selection it matches. Fixes PR16340.

llvm-svn: 252104
---
 clang/lib/Sema/SemaExpr.cpp         | 12 +++++++-----
 clang/test/Sema/generic-selection.c |  8 ++++++++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 857925da99c0..a4ca8a065cb4 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -1354,11 +1354,13 @@ Sema::CreateGenericSelectionExpr(SourceLocation KeyLoc,
                                  ArrayRef<Expr *> Exprs) {
   unsigned NumAssocs = Types.size();
   assert(NumAssocs == Exprs.size());
-  if (ControllingExpr->getType()->isPlaceholderType()) {
-    ExprResult result = CheckPlaceholderExpr(ControllingExpr);
-    if (result.isInvalid()) return ExprError();
-    ControllingExpr = result.get();
-  }
+
+  // Decay and strip qualifiers for the controlling expression type, and handle
+  // placeholder type replacement. See committee discussion from WG14 DR423.
+  ExprResult R = DefaultFunctionArrayLvalueConversion(ControllingExpr);
+  if (R.isInvalid())
+    return ExprError();
+  ControllingExpr = R.get();
 
   // The controlling expression is an unevaluated operand, so side effects are
   // likely unintended.
diff --git a/clang/test/Sema/generic-selection.c b/clang/test/Sema/generic-selection.c
index 8cef975c709c..0563ec0f4fc0 100644
--- a/clang/test/Sema/generic-selection.c
+++ b/clang/test/Sema/generic-selection.c
@@ -1,5 +1,7 @@
 // RUN: %clang_cc1 -std=c1x -fsyntax-only -verify %s
 
+void g(void);
+
 void foo(int n) {
   (void) _Generic(0,
       struct A: 0, // expected-error {{type 'struct A' in generic association incomplete}}
@@ -23,4 +25,10 @@ void foo(int n) {
   int a4[_Generic(0L, default: 1, short: 2, float: 3, int: 4) == 1 ? 1 : -1];
   int a5[_Generic(0, int: 1, short: 2, float: 3) == 1 ? 1 : -1];
   int a6[_Generic(0, short: 1, float: 2, int: 3) == 3 ? 1 : -1];
+
+  int a7[_Generic("test", char *: 1, default: 2) == 1 ? 1 : -1];
+  int a8[_Generic(g, void (*)(void): 1, default: 2) == 1 ? 1 : -1];
+
+  const int i = 12;
+  int a9[_Generic(i, int: 1, default: 2) == 1 ? 1 : -1];
 }