Re: C++ PATCH for c++/85883, class tmpl args deduction fail with new

[Marek Polacek <polacek at redhat dot com>]

On Fri, May 25, 2018 at 01:58:53PM -0400, Jason Merrill wrote:
> > +         /* For the rest, e.g. new A(1, 2, 3), create a list.  */
> > +         else if (len > 1)
> > +           {
> > +             unsigned int n;
> > +             tree t;
> > +             FOR_EACH_VEC_ELT (**init, n, t)
> > +               {
> > +                 t = resolve_nondeduced_context (t, complain);
> > +                 d_init = chainon (d_init, build_tree_list (NULL_TREE, t));
> 
> Using chainon here means that for each element, we have to walk the
> whole list to find the end.  See build_tree_list_vec.

Good point.  Fixed here:

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2018-05-29  Marek Polacek  <polacek@redhat.com>

	PR c++/85883
	* init.c (build_new): Handle deducing a class with new
	with more than one argument.

	* g++.dg/cpp1z/class-deduction55.C: New test.
	* g++.dg/cpp1z/class-deduction56.C: New test.
	* g++.dg/cpp1z/class-deduction57.C: New test.

diff --git gcc/cp/init.c gcc/cp/init.c
index 3f1e49bae21..da80e07f65b 100644
--- gcc/cp/init.c
+++ gcc/cp/init.c
@@ -3585,11 +3585,27 @@ build_new (vec<tree, va_gc> **placement, tree type, tree nelts,
       if (auto_node)
 	{
 	  tree d_init = NULL_TREE;
-	  if (vec_safe_length (*init) == 1)
+	  const size_t len = vec_safe_length (*init);
+	  /* E.g. new auto(x) must have exactly one element, or
+	     a {} initializer will have one element.  */
+	  if (len == 1)
 	    {
 	      d_init = (**init)[0];
 	      d_init = resolve_nondeduced_context (d_init, complain);
 	    }
+	  /* For the rest, e.g. new A(1, 2, 3), create a list.  */
+	  else if (len > 1)
+	    {
+	      unsigned int n;
+	      tree t;
+	      tree *pp = &d_init;
+	      FOR_EACH_VEC_ELT (**init, n, t)
+		{
+		  t = resolve_nondeduced_context (t, complain);
+		  *pp = build_tree_list (NULL_TREE, t);
+		  pp = &TREE_CHAIN (*pp);
+		}
+	    }
 	  type = do_auto_deduction (type, d_init, auto_node, complain);
 	}
     }
diff --git gcc/testsuite/g++.dg/cpp1z/class-deduction55.C gcc/testsuite/g++.dg/cpp1z/class-deduction55.C
index e69de29bb2d..a93d7203681 100644
--- gcc/testsuite/g++.dg/cpp1z/class-deduction55.C
+++ gcc/testsuite/g++.dg/cpp1z/class-deduction55.C
@@ -0,0 +1,15 @@
+// PR c++/85883
+// { dg-options -std=c++17 }
+
+template <typename T>
+struct Bar
+{
+  Bar(T) { }
+};
+
+int
+main ()
+{
+  auto x = Bar(1);
+  auto y = new Bar(3);
+}
diff --git gcc/testsuite/g++.dg/cpp1z/class-deduction56.C gcc/testsuite/g++.dg/cpp1z/class-deduction56.C
index e69de29bb2d..71dbfa1904d 100644
--- gcc/testsuite/g++.dg/cpp1z/class-deduction56.C
+++ gcc/testsuite/g++.dg/cpp1z/class-deduction56.C
@@ -0,0 +1,15 @@
+// PR c++/85883
+// { dg-options -std=c++17 }
+
+template <typename T1, typename T2>
+struct Bar
+{
+  Bar(T1, T2) { }
+};
+
+int
+main ()
+{
+  auto x = Bar(1, 2);
+  auto y = new Bar(3, 4);
+}
diff --git gcc/testsuite/g++.dg/cpp1z/class-deduction57.C gcc/testsuite/g++.dg/cpp1z/class-deduction57.C
index e69de29bb2d..200ba6c3536 100644
--- gcc/testsuite/g++.dg/cpp1z/class-deduction57.C
+++ gcc/testsuite/g++.dg/cpp1z/class-deduction57.C
@@ -0,0 +1,15 @@
+// PR c++/85883
+// { dg-options -std=c++17 }
+
+template <typename T1, typename T2, typename T3>
+struct Bar
+{
+  Bar(T1, T2, T3) { }
+};
+
+int
+main ()
+{
+  auto x = Bar(1, 2, 3);
+  auto y = new Bar(3, 4, 5);
+}