From 3f759575d3675150e665be997dd1e404e5c011f4 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Tue, 3 Apr 2018 13:41:06 -0400
Subject: [PATCH] Fix noexcept merging with system headers.

	* typeck.c (merge_types): Limit matching attribute shortcut to
	the default case.

From-SVN: r259042
---
 gcc/cp/ChangeLog                             |  5 +++++
 gcc/cp/typeck.c                              | 12 ++++++------
 gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C | 14 ++++++++++++++
 gcc/testsuite/g++.dg/cpp1z/noexcept-type19.h |  4 ++++
 4 files changed, 29 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/noexcept-type19.h

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ff3af26..405cf82 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2018-04-03  Jason Merrill  <jason@redhat.com>
+
+	* typeck.c (merge_types): Limit matching attribute shortcut to
+	the default case.
+
 2018-04-03  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/85147
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index d454c6c..e33f2c3 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -899,14 +899,14 @@ merge_types (tree t1, tree t2)
       return t1;
 
     default:;
+      if (attribute_list_equal (TYPE_ATTRIBUTES (t1), attributes))
+	return t1;
+      else if (attribute_list_equal (TYPE_ATTRIBUTES (t2), attributes))
+	return t2;
+      break;
     }
 
-  if (attribute_list_equal (TYPE_ATTRIBUTES (t1), attributes))
-    return t1;
-  else if (attribute_list_equal (TYPE_ATTRIBUTES (t2), attributes))
-    return t2;
-  else
-    return cp_build_type_attribute_variant (t1, attributes);
+  return cp_build_type_attribute_variant (t1, attributes);
 }
 
 /* Return the ARRAY_TYPE type without its domain.  */
diff --git a/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C b/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C
new file mode 100644
index 0000000..571c426
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.C
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++11 } }
+
+#include "noexcept-type19.h"
+
+extern "C" void *malloc (size_t);
+
+template<class T> void f(T*);
+
+void *g(size_t);
+
+int main()
+{
+  f<decltype(malloc)>(g);
+}
diff --git a/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.h b/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.h
new file mode 100644
index 0000000..33a2935
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/noexcept-type19.h
@@ -0,0 +1,4 @@
+#pragma GCC system_header
+
+typedef decltype(sizeof(0)) size_t;
+extern "C" void *malloc (size_t) throw();
-- 
2.7.4