r261669 - 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.

[Aaron Ballman via cfe-commits]

Author: aaronballman
Date: Tue Feb 23 12:55:15 2016
New Revision: 261669

URL: http://llvm.org/viewvc/llvm-project?rev=261669&view=rev
Log:
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.

Modified:
    cfe/trunk/lib/Sema/SemaExpr.cpp
    cfe/trunk/test/Sema/generic-selection.c

Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL: 
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=261669&r1=261668&r2=261669&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Tue Feb 23 12:55:15 2016
@@ -1373,10 +1373,13 @@ Sema::CreateGenericSelectionExpr(SourceL
 
   // 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.

Modified: cfe/trunk/test/Sema/generic-selection.c
URL: 
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/generic-selection.c?rev=261669&r1=261668&r2=261669&view=diff
==============================================================================
--- cfe/trunk/test/Sema/generic-selection.c (original)
+++ cfe/trunk/test/Sema/generic-selection.c Tue Feb 23 12:55:15 2016
@@ -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);
 }


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