re PR c++/52299 (GCC warns on compile time division by zero erroneously)

/cp
2012-03-12  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/52299
	* pt.c (tsubst_copy_and_build, case COND_EXPR): Avoid bogus
	division by zero warnings.

/testsuite
2012-03-12  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/52299
	* g++.dg/warn/Wdiv-by-zero-bogus.C: New.

From-SVN: r185264

gcc/cp/ChangeLog

+2012-03-12  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/52299
+	* pt.c (tsubst_copy_and_build, case COND_EXPR): Avoid bogus
+	division by zero warnings.
+
 2012-03-08  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* typeck.c (build_array_ref, cp_build_addr_expr_1, convert_ptrmem,

gcc/cp/pt.c

@@ -13943,11 +13943,35 @@ tsubst_copy_and_build (tree t,
       }
 
     case COND_EXPR:
-      return build_x_conditional_expr
-	(RECUR (TREE_OPERAND (t, 0)),
-	 RECUR (TREE_OPERAND (t, 1)),
-	 RECUR (TREE_OPERAND (t, 2)),
-         complain);
+      {
+	tree cond = RECUR (TREE_OPERAND (t, 0));
+	tree exp1, exp2;
+
+	if (TREE_CODE (cond) == INTEGER_CST)
+	  {
+	    if (integer_zerop (cond))
+	      {
+		++c_inhibit_evaluation_warnings;
+		exp1 = RECUR (TREE_OPERAND (t, 1));
+		--c_inhibit_evaluation_warnings;
+		exp2 = RECUR (TREE_OPERAND (t, 2));
+	      }
+	    else
+	      {
+		exp1 = RECUR (TREE_OPERAND (t, 1));
+		++c_inhibit_evaluation_warnings;
+		exp2 = RECUR (TREE_OPERAND (t, 2));
+		--c_inhibit_evaluation_warnings;
+	      }
+	  }
+	else
+	  {
+	    exp1 = RECUR (TREE_OPERAND (t, 1));
+	    exp2 = RECUR (TREE_OPERAND (t, 2));
+	  }
+
+	return build_x_conditional_expr (cond, exp1, exp2, complain);
+      }
 
     case PSEUDO_DTOR_EXPR:
       return finish_pseudo_destructor_expr

gcc/testsuite/ChangeLog

+2012-03-12  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/52299
+	* g++.dg/warn/Wdiv-by-zero-bogus.C: New.
+
 2012-03-12  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
 
 	PR tree-optimization/46728
@@ -18,7 +23,7 @@
 	* gcc.target/avr/torture/addr-space-0.h: New test.
 	* gcc.target/avr/torture/addr-space-1.h: New test.
 	* gcc.target/avr/torture/addr-space-x.h: New test.
-	
+
 2012-03-12  Andrew Pinski  <apinski@cavium.com>
 
 	* gcc.dg/tree-ssa/phi-opt-7.c: New testcase.

gcc/testsuite/g++.dg/warn/Wdiv-by-zero-bogus.C

+// PR c++/52299
+
+template<unsigned x>
+struct test0 {
+  static const unsigned a_
+  = x ? 10 / x : 10;
+};
+
+template<unsigned x>
+struct test1 {
+  static const unsigned a_
+  = !x ? 10 : 10 / x;
+};
+
+template<bool x>
+struct test2 {
+  static const unsigned a_
+  = x ? 10 / x : 10;
+};
+
+template<bool x>
+struct test3 {
+  static const unsigned a_
+  = !x ? 10 : 10 / x;
+};
+
+unsigned i0 = test0<0>::a_;
+unsigned i1 = test1<0>::a_;
+unsigned i2 = test2<false>::a_;
+unsigned i3 = test3<false>::a_;