From b4e93c5826ee7112463d2ed0ee9a4959b5362b78 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Wed, 17 Jan 2018 13:08:05 -0500
Subject: [PATCH] PR c++/81843 - ICE with variadic member template.

	PR c++/72801
	* pt.c (unify_pack_expansion): Don't try to deduce enclosing
	template args.

From-SVN: r256808
---
 gcc/cp/ChangeLog                         |  5 +++++
 gcc/cp/pt.c                              |  3 +++
 gcc/testsuite/g++.dg/cpp0x/variadic171.C | 12 ++++++++++++
 3 files changed, 20 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic171.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index a041f355e40..1cae4acaaca 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,10 @@
 2018-01-17  Jason Merrill  <jason@redhat.com>
 
+	PR c++/81843 - ICE with variadic member template.
+	PR c++/72801
+	* pt.c (unify_pack_expansion): Don't try to deduce enclosing
+	template args.
+
 	PR c++/82331 - ICE with variadic partial specialization of auto
 	* pt.c (unify) [TEMPLATE_PARM_INDEX]: Set processing_template_decl
 	around call to tsubst.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 9b5c35b4a21..5687bb21252 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -20068,6 +20068,7 @@ unify_pack_expansion (tree tparms, tree targs, tree packed_parms,
 
   /* Add in any args remembered from an earlier partial instantiation.  */
   targs = add_to_template_args (PACK_EXPANSION_EXTRA_ARGS (parm), targs);
+  int levels = TMPL_ARGS_DEPTH (targs);
 
   packed_args = expand_template_argument_pack (packed_args);
 
@@ -20083,6 +20084,8 @@ unify_pack_expansion (tree tparms, tree targs, tree packed_parms,
 
       /* Determine the index and level of this parameter pack.  */
       template_parm_level_and_index (parm_pack, &level, &idx);
+      if (level < levels)
+	continue;
 
       /* Keep track of the parameter packs and their corresponding
          argument packs.  */
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic171.C b/gcc/testsuite/g++.dg/cpp0x/variadic171.C
new file mode 100644
index 00000000000..1e268141d6d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic171.C
@@ -0,0 +1,12 @@
+// PR c++/81843
+// { dg-do compile { target c++11 } }
+
+template < typename > struct A;
+template < typename, typename > struct B;
+template < typename ... S > struct C
+{
+  template < typename > struct D {};
+  template < typename ... T > struct D < A < B < S, T > ... > >;
+};
+
+C <>::D < A < B < int, int > > > c;