From: Aaron Ballman <aaron@aaronballman.com>
Date: Tue, 23 Feb 2016 18:55:15 +0000 (+0000)
Subject: Amends r252104 to evaluate the controlling expression in an unevaluated context.... 
X-Git-Tag: llvmorg-3.9.0-rc1~13429
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=558995c9671d094a1e405084a181c9eddab04ec8;p=platform%2Fupstream%2Fllvm.git

Amends r252104 to evaluate the controlling expression in an unevaluated context. This eliminates false-positive diagnostics about null pointer dereferences (etc) in the controlling expression.

llvm-svn: 261669
---

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index bfbca29..ee9e646 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -1373,10 +1373,13 @@ Sema::CreateGenericSelectionExpr(SourceLocation KeyLoc,
 
   // 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();
+  {
+    EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
+    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 0563ec0..5c02005 100644
--- a/clang/test/Sema/generic-selection.c
+++ b/clang/test/Sema/generic-selection.c
@@ -31,4 +31,8 @@ void foo(int n) {
 
   const int i = 12;
   int a9[_Generic(i, int: 1, default: 2) == 1 ? 1 : -1];
+
+  // This is expected to not trigger any diagnostics because the controlling
+  // expression is not evaluated.
+  (void)_Generic(*(int *)0, int: 1);
 }