PR c++/87603 - constexpr functions are no longer noexcept.

	* constexpr.c (is_sub_constant_expr): Remove unused function.
	* cp-tree.h (is_sub_constant_expr): Remove declaration.
	* except.c (check_noexcept_r): Don't consider a call to a constexpr
	function noexcept.

	* g++.dg/cpp0x/constexpr-noexcept.C: Adjust the expected result.
	* g++.dg/cpp0x/constexpr-noexcept3.C: Likewise.
	* g++.dg/cpp0x/constexpr-noexcept4.C: Likewise.
	* g++.dg/cpp0x/constexpr-noexcept8.C: New test.
	* g++.dg/cpp0x/inh-ctor32.C: Remove dg-message.
	* g++.dg/cpp1y/constexpr-noexcept1.C: New test.

From-SVN: r270320

4 files changed, 14 insertions, 27 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 9a12622..8e63fda 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -3,6 +3,12 @@
 	* except.c (build_noexcept_spec): Use build_converted_constant_bool_expr
 	instead of perform_implicit_conversion_flags.
 
+	PR c++/87603 - constexpr functions are no longer noexcept.
+	* constexpr.c (is_sub_constant_expr): Remove unused function.
+	* cp-tree.h (is_sub_constant_expr): Remove declaration.
+	* except.c (check_noexcept_r): Don't consider a call to a constexpr
+	function noexcept.
+
 2019-04-11  Jakub Jelinek  <jakub@redhat.com>
 
 	PR translation/90035
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 0ce5618..9c13f0d 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -5423,27 +5423,6 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant,
   return r;
 }
 
-/* Returns true if T is a valid subexpression of a constant expression,
-   even if it isn't itself a constant expression.  */
-
-bool
-is_sub_constant_expr (tree t)
-{
-  bool non_constant_p = false;
-  bool overflow_p = false;
-  hash_map <tree, tree> map;
-  HOST_WIDE_INT constexpr_ops_count = 0;
-
-  constexpr_ctx ctx
-    = { NULL, &map, NULL, NULL, NULL, NULL, &constexpr_ops_count,
-	true, true, false };
-
-  instantiate_constexpr_fns (t);
-  cxx_eval_constant_expression (&ctx, t, false, &non_constant_p,
-				&overflow_p);
-  return !non_constant_p && !overflow_p;
-}
-
 /* If T represents a constant expression returns its reduced value.
    Otherwise return error_mark_node.  If T is dependent, then
    return NULL.  */
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index b87b968..ff4ce06 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7720,7 +7720,6 @@ extern tree fold_non_dependent_init		(tree,
 						 tsubst_flags_t = tf_warning_or_error,
 						 bool = false);
 extern tree fold_simple				(tree);
-extern bool is_sub_constant_expr                (tree);
 extern bool reduced_constant_expression_p       (tree);
 extern bool is_instantiation_of_constexpr       (tree);
 extern bool var_in_constexpr_fn                 (tree);
diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index 25ab869..afc2610 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -1128,11 +1128,14 @@ check_noexcept_r (tree *tp, int * /*walk_subtrees*/, void * /*data*/)
 	      && (DECL_ARTIFICIAL (fn)
 		  || nothrow_libfn_p (fn)))
 	    return TREE_NOTHROW (fn) ? NULL_TREE : fn;
-	  /* A call to a constexpr function is noexcept if the call
-	     is a constant expression.  */
-	  if (DECL_DECLARED_CONSTEXPR_P (fn)
-	      && is_sub_constant_expr (t))
-	    return NULL_TREE;
+	  /* We used to treat a call to a constexpr function as noexcept if
+	     the call was a constant expression (CWG 1129).  This has changed
+	     in P0003 whereby noexcept has no special rule for constant
+	     expressions anymore.  Since the current behavior is important for
+	     certain library functionality, we treat this as a DR, therefore
+	     adjusting the behavior for C++11 and C++14.  Previously, we had
+	     to evaluate the noexcept-specifier's operand here, but that could
+	     cause instantiations that would fail.  */
 	}
       if (!TYPE_NOTHROW_P (type))
 	return fn;