Class template argument deduction in new-expression

[gcc.git] / gcc / cp / init.c

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 55209634147777b08c4acc95567510644258ca8e..191fe13e31039947d1d5d660eef0b9c0d8d9ba94 100644 (file)
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -1217,6 +1217,12 @@ emit_mem_initializers (tree mem_inits)
        /* C++14 DR1658 Means we do not have to construct vbases of
           abstract classes.  */
        construct_virtual_base (subobject, arguments);
+      else
+       /* When not constructing vbases of abstract classes, at least mark
+          the arguments expressions as read to avoid
+          -Wunused-but-set-parameter false positives.  */
+       for (tree arg = arguments; arg; arg = TREE_CHAIN (arg))
+         mark_exp_read (TREE_VALUE (arg));
 
       if (inherited_base)
        pop_deferring_access_checks ();
@@ -3472,15 +3478,19 @@ build_new (vec<tree, va_gc> **placement, tree type, tree nelts,
   if (type == error_mark_node)
     return error_mark_node;
 
-  if (nelts == NULL_TREE && vec_safe_length (*init) == 1
+  if (nelts == NULL_TREE
       /* Don't do auto deduction where it might affect mangling.  */
       && (!processing_template_decl || at_function_scope_p ()))
     {
       tree auto_node = type_uses_auto (type);
       if (auto_node)
        {
-         tree d_init = (**init)[0];
-         d_init = resolve_nondeduced_context (d_init, complain);
+         tree d_init = NULL_TREE;
+         if (vec_safe_length (*init) == 1)
+           {
+             d_init = (**init)[0];
+             d_init = resolve_nondeduced_context (d_init, complain);
+           }
          type = do_auto_deduction (type, d_init, auto_node);
        }
     }