From 99547487e15637ef6ef7d3f39236fabee54cab4d Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Wed, 17 Jan 2018 13:07:53 -0500
Subject: [PATCH] PR c++/82331 - ICE with variadic partial specialization of
 auto

	* pt.c (unify) [TEMPLATE_PARM_INDEX]: Set processing_template_decl
	around call to tsubst.

From-SVN: r256807
---
 gcc/cp/ChangeLog                            |  4 ++++
 gcc/cp/pt.c                                 |  2 ++
 gcc/testsuite/g++.dg/cpp1z/nontype-auto13.C | 18 ++++++++++++++++++
 3 files changed, 24 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/nontype-auto13.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index bbe31ec7693..a041f355e40 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,9 @@
 2018-01-17  Jason Merrill  <jason@redhat.com>
 
+	PR c++/82331 - ICE with variadic partial specialization of auto
+	* pt.c (unify) [TEMPLATE_PARM_INDEX]: Set processing_template_decl
+	around call to tsubst.
+
 	PR c++/82760 - memory corruption with aligned new.
 	* call.c (build_operator_new_call): Update *args if we add the
 	align_arg.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 61fe2a3a14d..9b5c35b4a21 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -20686,7 +20686,9 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict,
 	 template-parameter exactly, except that a template-argument
 	 deduced from an array bound may be of any integral type.
 	 The non-type parameter might use already deduced type parameters.  */
+      ++processing_template_decl;
       tparm = tsubst (TREE_TYPE (parm), targs, 0, NULL_TREE);
+      --processing_template_decl;
       if (tree a = type_uses_auto (tparm))
 	{
 	  tparm = do_auto_deduction (tparm, arg, a, complain, adc_unify);
diff --git a/gcc/testsuite/g++.dg/cpp1z/nontype-auto13.C b/gcc/testsuite/g++.dg/cpp1z/nontype-auto13.C
new file mode 100644
index 00000000000..2152cef811e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/nontype-auto13.C
@@ -0,0 +1,18 @@
+// PR c++/82331
+// { dg-options -std=c++17 }
+
+template <auto>
+class X;
+
+template <typename R, typename... A, R (*F) (A...)>
+class X<F> {
+public:
+    static R call (A... args)
+    {
+        return (*F)(args...);
+    }
+};
+
+int func (int a, int b) { return a + b; }
+
+int test () { return X<&func>::call(1, 2); }