From 96176bb3f185bdb1251f1b427c2a50b0088ac80f Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Wed, 18 Jan 2017 12:52:24 +0000
Subject: [PATCH] cp-tree.h: Clarify exception spec node comment.

	* cp-tree.h: Clarify exception spec node comment.
	* except.c (nothrow_spec_p): Simplify by checking node-equality.

From-SVN: r244576
---
 gcc/cp/ChangeLog |  3 +++
 gcc/cp/cp-tree.h |  3 ++-
 gcc/cp/except.c  | 16 +++++++++-------
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 7733be7cc52..32bf9e36070 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,8 @@
 2017-01-18  Nathan Sidwell  <nathan@acm.org>
 
+	* cp-tree.h: Clarify exception spec node comment.
+	* except.c (nothrow_spec_p): Simplify by checking node-equality.
+
 	PR c++/79091
 	* mangle.c (write_exception_spec): Check nothrow explicitly.
 	(write_encoding): Don't increment processing_template_decl around
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 0c8f147c6b2..98e4cbd05de 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1212,7 +1212,8 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
 #define lang_name_c			cp_global_trees[CPTI_LANG_NAME_C]
 #define lang_name_cplusplus		cp_global_trees[CPTI_LANG_NAME_CPLUSPLUS]
 
-/* Exception specifier used for throw().  */
+/* Exception specifiers used for throw(), noexcept(true) and
+   noexcept(false).  We rely on these being uncloned.  */
 #define empty_except_spec		cp_global_trees[CPTI_EMPTY_EXCEPT_SPEC]
 #define noexcept_true_spec		cp_global_trees[CPTI_NOEXCEPT_TRUE_SPEC]
 #define noexcept_false_spec		cp_global_trees[CPTI_NOEXCEPT_FALSE_SPEC]
diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index 034c35a4888..bfc32908aec 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -1143,15 +1143,17 @@ bool
 nothrow_spec_p (const_tree spec)
 {
   gcc_assert (!DEFERRED_NOEXCEPT_SPEC_P (spec));
-  if (spec == NULL_TREE
-      || TREE_VALUE (spec) != NULL_TREE
-      || spec == noexcept_false_spec)
-    return false;
-  if (TREE_PURPOSE (spec) == NULL_TREE
+
+  if (spec == empty_except_spec
       || spec == noexcept_true_spec)
     return true;
-  gcc_assert (processing_template_decl
-	      || TREE_PURPOSE (spec) == error_mark_node);
+
+  gcc_assert (!spec
+	      || TREE_VALUE (spec)
+	      || spec == noexcept_false_spec
+	      || TREE_PURPOSE (spec) == error_mark_node
+	      || processing_template_decl);
+
   return false;
 }
 
-- 
2.30.2