Fix PR c++/69056 (argument pack deduction failure during overload resolution)

gcc/cp/ChangeLog:

	PR c++/69056
	* pt.c (try_one_overload): Handle comparing argument packs so
	that there is no conflict if we deduced more arguments of an
	argument pack than were explicitly specified.

gcc/testsuite/ChangeLog:

	PR c++/69056
	g++.dg/cpp0x/pr69056.C: New test.

From-SVN: r233108

4 files changed, 64 insertions, 0 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 804deb0..6ac9a64 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2016-02-03  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/69056
+	* pt.c (try_one_overload): Handle comparing argument packs so
+	that there is no conflict if we deduced more arguments of an
+	argument pack than were explicitly specified.
+
 2016-01-31  Jakub Jelinek  <jakub@redhat.com>
 	    Jason Merrill  <jason@redhat.com>
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 27dfdf86..9cde9c7 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -18736,6 +18736,28 @@ try_one_overload (tree tparms,
 	   template args used in the function parm list with our own
 	   template parms.  Discard them.  */
 	TREE_VEC_ELT (tempargs, i) = NULL_TREE;
+      else if (oldelt && ARGUMENT_PACK_P (oldelt))
+	{
+	  /* Check that the argument at each index of the deduced argument pack
+	     is equivalent to the corresponding explicitly specified argument.
+	     We may have deduced more arguments than were explicitly specified,
+	     and that's OK.  */
+	  gcc_assert (ARGUMENT_PACK_INCOMPLETE_P (oldelt));
+	  gcc_assert (ARGUMENT_PACK_ARGS (oldelt)
+		      == ARGUMENT_PACK_EXPLICIT_ARGS (oldelt));
+
+	  tree explicit_pack = ARGUMENT_PACK_ARGS (oldelt);
+	  tree deduced_pack = ARGUMENT_PACK_ARGS (elt);
+
+	  if (TREE_VEC_LENGTH (deduced_pack)
+	      < TREE_VEC_LENGTH (explicit_pack))
+	    return 0;
+
+	  for (int j = 0; j < TREE_VEC_LENGTH (explicit_pack); j++)
+	    if (!template_args_equal (TREE_VEC_ELT (explicit_pack, j),
+				      TREE_VEC_ELT (deduced_pack, j)))
+	      return 0;
+	}
       else if (oldelt && !template_args_equal (oldelt, elt))
 	return 0;
     }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5bee447..1a17a9d 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-02-03  Patrick Palka  <ppalka@gcc.gnu.org>
+
+	PR c++/69056
+	g++.dg/cpp0x/pr69056.C: New test.
+
 2016-02-03  Vladimir Makarov  <vmakarov@redhat.com>
 	    Alexandre Oliva  <aoliva@redhat.com>
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/pr69056.C b/gcc/testsuite/g++.dg/cpp0x/pr69056.C
new file mode 100644
index 0000000..ab4e071
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/pr69056.C
@@ -0,0 +1,30 @@
+// { dg-do compile { target c++11 } }
+// PR c++/69056
+
+template <typename T, typename... Args>
+void resolver(int (*) (T, Args...));
+
+int funcA(int, float) { return 0; }
+int funcA(double) { return 0; }
+
+int funcB(int, float, char) { return 0; }
+int funcB(int, bool) { return 0; }
+int funcB(double) { return 0; }
+
+int funcC(int) { return 0; }
+int funcC(double) { return 0; }
+
+void
+foo (void)
+{
+  resolver (&funcA); // { dg-error "no match" }
+  resolver<int> (&funcA);
+  resolver<double> (&funcA);
+
+  resolver<int> (&funcB); // { dg-error "no match" }
+  resolver<int, char> (&funcB); // { dg-error "no match" }
+  resolver<int, float> (&funcB);
+
+  resolver<int> (&funcC);
+  resolver<int, float> (&funcC); // { dg-error "no match" }
+}