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-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=1dc827614f4762cb4135bfa1ae0b7d628ed8f1a2;p=clang

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.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@261669 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index bfbca298ce..ee9e646e24 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/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/test/Sema/generic-selection.c b/test/Sema/generic-selection.c
index 0563ec0f4f..5c02005d0f 100644
--- a/test/Sema/generic-selection.c
+++ b/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);
 }