From 05c602a135224b1fbc573fc54e3c925196503187 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Tue, 10 Apr 2018 10:23:54 -0400
Subject: [PATCH] PR c++/85285 - ICE with flexible array after substitution.

	* pt.c (instantiate_class_template_1): Check for flexible array in
	union.

From-SVN: r259277
---
 gcc/cp/ChangeLog                     | 6 ++++++
 gcc/cp/pt.c                          | 8 ++++++++
 gcc/testsuite/g++.dg/ext/flexary30.C | 8 ++++++++
 3 files changed, 22 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/flexary30.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 33f0c37a3cd..43592502c6f 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2018-04-10  Jason Merrill  <jason@redhat.com>
+
+	PR c++/85285 - ICE with flexible array after substitution.
+	* pt.c (instantiate_class_template_1): Check for flexible array in
+	union.
+
 2018-04-09  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/85227
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index db3d7e38d85..76e546cdeaa 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -10904,6 +10904,14 @@ instantiate_class_template_1 (tree type)
 			      cxx_incomplete_type_error (r, rtype);
 			      TREE_TYPE (r) = error_mark_node;
 			    }
+			  else if (TREE_CODE (rtype) == ARRAY_TYPE
+				   && TYPE_DOMAIN (rtype) == NULL_TREE
+				   && (TREE_CODE (type) == UNION_TYPE
+				       || TREE_CODE (type) == QUAL_UNION_TYPE))
+			    {
+			      error ("flexible array member %qD in union", r);
+			      TREE_TYPE (r) = error_mark_node;
+			    }
 			}
 
 		      /* If it is a TYPE_DECL for a class-scoped ENUMERAL_TYPE,
diff --git a/gcc/testsuite/g++.dg/ext/flexary30.C b/gcc/testsuite/g++.dg/ext/flexary30.C
new file mode 100644
index 00000000000..59b7587594c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/flexary30.C
@@ -0,0 +1,8 @@
+// PR c++/85285
+
+template<typename T> union A
+{
+  T x;				// { dg-error "flexible array" }
+};
+
+A<int[]> a;
-- 
2.30.2