re PR c++/46977 ([C++0x] ICE: SIGSEGV in htab_find_slot_with_hash (hashtab.c:650))

	PR c++/46977
	* semantics.c (potential_constant_expression_1): Split out from
	potential_constant_expression.  Add want_rval parm.  Handle
	template expression forms.  Don't enforce restriction on address
	of automatic variable here.  Add a couple of diagnostics that
	had been missing.
	(require_potential_constant_expression): New entry point.
	(build_data_member_initialization, register_constexpr_fundef): Adjust.
	(maybe_constant_value): Check potential_constant_expression.
	* pt.c (fold_non_dependent_expr_sfinae): Likewise.
	* tree.c (build_vec_init_expr): Adjust.

From-SVN: r169096

gcc/cp/ChangeLog

+2011-01-21  Jason Merrill  <jason@redhat.com>
+
+	PR c++/46977
+	* semantics.c (potential_constant_expression_1): Split out from
+	potential_constant_expression.  Add want_rval parm.  Handle
+	template expression forms.  Don't enforce restriction on address
+	of automatic variable here.  Add a couple of diagnostics that
+	had been missing.
+	(require_potential_constant_expression): New entry point.
+	(build_data_member_initialization, register_constexpr_fundef): Adjust.
+	(maybe_constant_value): Check potential_constant_expression.
+	* pt.c (fold_non_dependent_expr_sfinae): Likewise.
+	* tree.c (build_vec_init_expr): Adjust.
+
 2011-01-19  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/47303

gcc/cp/cp-tree.h

@@ -5245,7 +5245,8 @@ extern tree validate_constexpr_fundecl (tree);
 extern tree register_constexpr_fundef (tree, tree);
 extern bool check_constexpr_ctor_body (tree, tree);
 extern tree ensure_literal_type_for_constexpr_object (tree);
-extern bool potential_constant_expression (tree, tsubst_flags_t);
+extern bool potential_constant_expression (tree);
+extern bool require_potential_constant_expression (tree);
 extern tree cxx_constant_value (tree);
 extern tree maybe_constant_value (tree);
 extern tree maybe_constant_init (tree);

gcc/cp/pt.c

@@ -5159,6 +5159,7 @@ fold_non_dependent_expr_sfinae (tree expr, tsubst_flags_t complain)
      as two declarations of the same function, for example.  */
   if (processing_template_decl
       && !type_dependent_expression_p (expr)
+      && potential_constant_expression (expr)
       && !value_dependent_expression_p (expr))
     {
       HOST_WIDE_INT saved_processing_template_decl;
@@ -17964,11 +17965,11 @@ dependent_scope_p (tree scope)
    [temp.dep.constexpr].  EXPRESSION is already known to be a constant
    expression.  */
 
-/* FIXME this predicate is not appropriate for general expressions; the
-   predicates we want instead are "valid constant expression, value
-   dependent or not?", "really constant expression, not value dependent?"
-   and "instantiation-dependent?".  Try to integrate with
-   potential_constant_expression?
+/* Note that this predicate is not appropriate for general expressions;
+   only constant expressions (that satisfy potential_constant_expression)
+   can be tested for value dependence.
+
+   We should really also have a predicate for "instantiation-dependent".
 
    fold_non_dependent_expr: fold if constant and not type-dependent and not value-dependent.
      (what about instantiation-dependent constant-expressions?)

gcc/cp/tree.c

@@ -513,9 +513,13 @@ build_vec_init_expr (tree type, tree init)
   SET_EXPR_LOCATION (init, input_location);
 
   if (current_function_decl
-      && DECL_DECLARED_CONSTEXPR_P (current_function_decl)
-      && potential_constant_expression (elt_init, tf_warning_or_error))
-    VEC_INIT_EXPR_IS_CONSTEXPR (init) = true;
+      && DECL_DECLARED_CONSTEXPR_P (current_function_decl))
+    {
+      if (potential_constant_expression (elt_init))
+	VEC_INIT_EXPR_IS_CONSTEXPR (init) = true;
+      else if (!processing_template_decl)
+	require_potential_constant_expression (elt_init);
+    }
   VEC_INIT_EXPR_VALUE_INIT (init) = value_init;
 
   init = build_target_expr (slot, init);

gcc/testsuite/ChangeLog

+2011-01-21  Jason Merrill  <jason@redhat.com>
+
+	* g++.dg/cpp0x/constexpr-stmtexpr.C: New.
+
 2011-01-21  Jeff Law <law@redhat.com>
 
 	PR rtl-optimization/41619

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

+// PR c++/46977
+// { dg-options "-std=c++0x" }
+
+template < typename > void
+foo ()
+{
+  ({int i;}), 0;
+}