Patchwork C++ PATCH for c++/48424 (function parameter packs not at the end of the list)

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Submitter Jason Merrill
Date May 26, 2011, 1:20 p.m.
Message ID <4DDE53A2.1090407@redhat.com>
Download mbox | patch
Permalink /patch/97574/
State New
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Comments

Jason Merrill - May 26, 2011, 1:20 p.m.
The initial specification of variadic templates required function 
parameter packs to be at the end of the parameter list, but that 
restriction was soon found to be undesirable; this patch updates G++ to 
support packs earlier in the parameter list as specified in the FDIS.

Tested x86_64-pc-linux-gnu, applying to trunk.

Patch

commit 4903fd6cbf099822f15e6af2708ab5d54e7eae18
Author: Jason Merrill <jason@redhat.com>
Date:   Wed May 25 23:15:19 2011 -0400

    	PR c++/48424
    	* decl.c (grokparms): Function parameter packs don't need to
    	go at the end.
    	* pt.c (type_unification_real): But they aren't deduced otherwise.

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 8ab0c8a..a956dbb 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -10551,12 +10551,6 @@  grokparms (tree parmlist, tree *parms)
 	    init = check_default_argument (decl, init);
 	}
 
-      if (TREE_CODE (decl) == PARM_DECL
-          && FUNCTION_PARAMETER_PACK_P (decl)
-          && TREE_CHAIN (parm)
-          && TREE_CHAIN (parm) != void_list_node)
-        error ("parameter packs must be at the end of the parameter list");
-
       DECL_CHAIN (decl) = decls;
       decls = decl;
       result = tree_cons (init, type, result);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index c9c25cd..ab48c8f 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -14262,11 +14262,24 @@  type_unification_real (tree tparms,
   while (parms && parms != void_list_node
 	 && ia < nargs)
     {
-      if (TREE_CODE (TREE_VALUE (parms)) == TYPE_PACK_EXPANSION)
-        break;
-
       parm = TREE_VALUE (parms);
+
+      if (TREE_CODE (parm) == TYPE_PACK_EXPANSION
+	  && (!TREE_CHAIN (parms) || TREE_CHAIN (parms) == void_list_node))
+	/* For a function parameter pack that occurs at the end of the
+	   parameter-declaration-list, the type A of each remaining
+	   argument of the call is compared with the type P of the
+	   declarator-id of the function parameter pack.  */
+	break;
+
       parms = TREE_CHAIN (parms);
+
+      if (TREE_CODE (parm) == TYPE_PACK_EXPANSION)
+	/* For a function parameter pack that does not occur at the
+	   end of the parameter-declaration-list, the type of the
+	   parameter pack is a non-deduced context.  */
+	continue;
+
       arg = args[ia];
       ++ia;
       arg_expr = NULL;
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic111.C b/gcc/testsuite/g++.dg/cpp0x/variadic111.C
new file mode 100644
index 0000000..378162e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic111.C
@@ -0,0 +1,19 @@ 
+// PR c++/48424
+// { dg-options -std=c++0x }
+
+template<typename... Args1>
+struct S
+{
+  template<typename... Args2>
+    void f(Args1... args1, Args2&&... args2)
+    {
+    }
+};
+
+int main()
+{
+  S<int, double> s;
+  s.f(1,2.0,false,'a');
+}
+
+// { dg-final { scan-assembler "_ZN1SIIidEE1fIIbcEEEvidDpOT_" } }
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic41.C b/gcc/testsuite/g++.dg/cpp0x/variadic41.C
index d209766..9cfd847 100644
--- a/gcc/testsuite/g++.dg/cpp0x/variadic41.C
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic41.C
@@ -1,3 +1,14 @@ 
+// A function parameter pack is only deduced if it's at the end
 // { dg-options "-std=gnu++0x" }
 template<typename... Args>
-void f(const Args&... args, int oops); // { dg-error "end" }
+void f(const Args&... args, int oops);
+
+int main()
+{
+  f<>(1);
+  f(1);
+  f<int>(1,2);
+  f(1,2);			// { dg-error "no match" }
+}
+
+// { dg-prune-output "note" }