re PR c++/63265 (Constexpr variables can trigger spurious compiler warnings)

/cp
2014-11-11  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/63265
	* pt.c (tsubst_copy_and_build, case COND_EXPR): Maybe fold to
	constant the condition.

/testsuite
2014-11-11  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/63265
	* g++.dg/cpp0x/constexpr-63265.C: New.

From-SVN: r217361

gcc/cp/ChangeLog

+2014-11-11  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/63265
+	* pt.c (tsubst_copy_and_build, case COND_EXPR): Maybe fold to
+	constant the condition.
+
 2014-11-10  Andi Kleen  <ak@linux.intel.com>
 
 	* semantics.c (finish_goto_stmt): Call check_no_cilk.

gcc/cp/pt.c

@@ -15138,11 +15138,13 @@ tsubst_copy_and_build (tree t,
     case COND_EXPR:
       {
 	tree cond = RECUR (TREE_OPERAND (t, 0));
+	tree folded_cond = (maybe_constant_value
+			    (fold_non_dependent_expr_sfinae (cond, tf_none)));
 	tree exp1, exp2;
 
-	if (TREE_CODE (cond) == INTEGER_CST)
+	if (TREE_CODE (folded_cond) == INTEGER_CST)
 	  {
-	    if (integer_zerop (cond))
+	    if (integer_zerop (folded_cond))
 	      {
 		++c_inhibit_evaluation_warnings;
 		exp1 = RECUR (TREE_OPERAND (t, 1));
@@ -15156,6 +15158,7 @@ tsubst_copy_and_build (tree t,
 		exp2 = RECUR (TREE_OPERAND (t, 2));
 		--c_inhibit_evaluation_warnings;
 	      }
+	    cond = folded_cond;
 	  }
 	else
 	  {

gcc/testsuite/ChangeLog

+2014-11-11  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/63265
+	* g++.dg/cpp0x/constexpr-63265.C: New.
+
 2014-11-11  Evgeny Stupachenko  <evstupac@gmail.com>
 
 	* gcc.target/i386/pr52252-atom-1.c: New.

gcc/testsuite/g++.dg/cpp0x/constexpr-63265.C

+// PR c++/63265
+// { dg-do compile { target c++11 } }
+
+#define LSHIFT (sizeof(unsigned int) * __CHAR_BIT__)
+
+template <int lshift>
+struct SpuriouslyWarns1 {
+    static constexpr unsigned int v = lshift < LSHIFT ? 1U << lshift : 0;
+};
+
+static_assert(SpuriouslyWarns1<LSHIFT>::v == 0, "Impossible occurred");
+
+template <int lshift>
+struct SpuriouslyWarns2 {
+    static constexpr bool okay = lshift < LSHIFT;
+    static constexpr unsigned int v = okay ? 1U << lshift : 0;
+};
+
+static_assert(SpuriouslyWarns2<LSHIFT>::v == 0, "Impossible occurred");