re PR c++/54020 ([c++0x] incorrectly accepted constexpr functions)

	PR c++/54020
	* semantics.c (potential_constant_expression_1) [COND_EXPR]: Call
	maybe_constant_value.

From-SVN: r189851

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index e7b47111e264474f7971b8262969803c266bf098..f5fbb5cf7db4859db17f090c0ec0fa3bae1bc11a 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,9 @@
 2012-07-25  Jason Merrill  <jason@redhat.com>
 
+       PR c++/54020
+       * semantics.c (potential_constant_expression_1) [COND_EXPR]: Call
+       maybe_constant_value.
+
        * cp-tree.h (tsubst_flags): Remove tf_no_access_control.
        * call.c (standard_conversion): Don't set it.
        * class.c (resolve_address_of_overloaded_function): Don't check it.

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 6381949a664902b056ba3e714d5b4ae80376cb1c..b27e8ab128b74e49a8040c632d9a6e9f798d0fb6 100644 (file)
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -8497,10 +8497,17 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
     case TRUTH_ORIF_EXPR:
       tmp = boolean_false_node;
     truth:
-      if (TREE_OPERAND (t, 0) == tmp)
-       return potential_constant_expression_1 (TREE_OPERAND (t, 1), rval, flags);
-      else
-       return potential_constant_expression_1 (TREE_OPERAND (t, 0), rval, flags);
+      {
+       tree op = TREE_OPERAND (t, 0);
+       if (!potential_constant_expression_1 (op, rval, flags))
+         return false;
+       if (!processing_template_decl)
+         op = maybe_constant_value (op);
+       if (tree_int_cst_equal (op, tmp))
+         return potential_constant_expression_1 (TREE_OPERAND (t, 1), rval, flags);
+       else
+         return true;
+      }
 
     case PLUS_EXPR:
     case MULT_EXPR:
@@ -8556,7 +8563,9 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
       tmp = TREE_OPERAND (t, 0);
       if (!potential_constant_expression_1 (tmp, rval, flags))
        return false;
-      else if (integer_zerop (tmp))
+      if (!processing_template_decl)
+       tmp = maybe_constant_value (tmp);
+      if (integer_zerop (tmp))
        return potential_constant_expression_1 (TREE_OPERAND (t, 2),
                                                want_rval, flags);
       else if (TREE_CODE (tmp) == INTEGER_CST)

diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-neg2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-neg2.C
new file mode 100644 (file)
index 0000000..793b4c3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-neg2.C
@@ -0,0 +1,27 @@
+// PR c++/54020
+// { dg-do compile { target c++11 } }
+
+// Preliminaries.
+extern int nonconst_func(int);
+constexpr int identity(int x) { return x; }
+constexpr int zero() { return identity(0); }
+constexpr int one() { return identity(1); }
+
+// Correctly accepted.
+constexpr int three = one() ? 3 : nonconst_func(0);
+
+// Incorrectly accepted.  See [dcl.constexpr] #5:
+//   For a constexpr function, if no function argument values exist
+//   such that the function invocation sub-stitution would produce a
+//   constant expression (5.19), the program is ill-formed; no diagnostic
+//   required.
+constexpr int bogus() { return zero () ? 3 : nonconst_func(0); } // { dg-error "nonconst_func" }
+
+// Correctly rejected (not sure why).
+constexpr int correct_error() { return nonconst_func(0); } // { dg-error "nonconst_func" }
+
+// Correctly rejected.
+constexpr int z = bogus();     // { dg-error "" }
+
+// This is also correctly rejected.
+constexpr int correct_failure() { return 0 ? 3 : nonconst_func(0); } // { dg-error "nonconst_func" }