Re: [C++ Patch] PR 51911 V2 ("G++ accepts new auto { list }")

[Paolo Carlini]

... concretely, I tested successfully the below.

Thanks,
Paolo.


Index: cp/parser.c
===
--- cp/parser.c (revision 227737)
+++ cp/parser.c (working copy)
@@ -7591,8 +7591,9 @@ cp_parser_new_expression (cp_parser* parser)
 type = cp_parser_new_type_id (parser, );
 
   /* If the next token is a `(' or '{', then we have a new-initializer.  */
-  if (cp_lexer_next_token_is (parser->lexer, CPP_OPEN_PAREN)
-  || cp_lexer_next_token_is (parser->lexer, CPP_OPEN_BRACE))
+  cp_token *token = cp_lexer_peek_token (parser->lexer);
+  if (token->type == CPP_OPEN_PAREN
+  || token->type == CPP_OPEN_BRACE)
 initializer = cp_parser_new_initializer (parser);
   else
 initializer = NULL;
@@ -7601,6 +7602,21 @@ cp_parser_new_expression (cp_parser* parser)
  expression.  */
   if (cp_parser_non_integral_constant_expression (parser, NIC_NEW))
 ret = error_mark_node;
+  /* 5.3.4/2: "If the auto type-specifier appears in the type-specifier-seq
+ of a new-type-id or type-id of a new-expression, the new-expression shall
+ contain a new-initializer of the form ( assignment-expression )".
+ Additionally, consistently with the spirit of DR 1467, we want to accept
+ 'new auto { 2 }' too.  */
+  else if (type_uses_auto (type)
+  && (vec_safe_length (initializer) != 1
+  || (BRACE_ENCLOSED_INITIALIZER_P ((*initializer)[0])
+  && CONSTRUCTOR_NELTS ((*initializer)[0]) != 1)))
+{
+  error_at (token->location,
+   "initialization of new-expression for type % "
+   "requires exactly one element");
+  ret = error_mark_node;
+}
   else
 {
   /* Create a representation of the new-expression.  */
Index: testsuite/g++.dg/cpp0x/new-auto1.C
===
--- testsuite/g++.dg/cpp0x/new-auto1.C  (revision 0)
+++ testsuite/g++.dg/cpp0x/new-auto1.C  (working copy)
@@ -0,0 +1,10 @@
+// PR c++/51911
+// { dg-do compile { target c++11 } }
+
+#include 
+
+auto foo1 = new auto { 3, 4, 5 };  // { dg-error "22:initialization of 
new-expression for type 'auto'" }
+auto bar1 = new auto { 2 };
+
+auto foo2 = new auto ( 3, 4, 5 );  // { dg-error "22:initialization of 
new-expression for type 'auto'" }
+auto bar2 = new auto ( 2 );

Re: [C++ Patch] PR 51911 V2 ("G++ accepts new auto { list }")

[Jason Merrill]

OK.

Jason

Re: [C++ Patch] PR 51911 V2 ("G++ accepts new auto { list }")

[Paolo Carlini]

Hi,

On 09/11/2015 10:05 PM, Jason Merrill wrote:

On 09/11/2015 03:11 PM, Paolo Carlini wrote:

this is a slightly reworked (simplified) version of a patch I sent a
while ago. The issue is that we are not enforcing at all 5.3.4/2 in the
parser, thus we end up rejecting the first test below with a misleading
error message talking about list-initialization (and a wrong location),
because we diagnose it too late like 'auto foo{3, 4, 5};', and simply
accepting the second. Tested x86_64-linux.


Hmm, I think we really ought to accept

  new auto { 2 }

to be consistent with all the other recent changes to treat { elt } 
like (elt); this seems like a piece that was missed from DR 1467.  Do 
you agree, Ville?
I see, while waiting for Ville, maybe I can ask what we should do in 
case he agrees. The error message we currently emit for new auto { 3, 4, 
5 } seems suboptimal in various ways:


51911.C:6:31: error: direct-list-initialization of ‘auto’ requires 
exactly one element [-fpermissive]

 auto foo = new auto { 3, 4, 5 };
   ^
51911.C:6:31: note: for deduction to ‘std::initializer_list’, use 
copy-list-initialization (i.e. add ‘=’ before the ‘{’)


the caret is under the last '}' and the note doesn't make much sense (of 
course do_auto_deduction doesn't know we are handling a new). Thus I 
wonder if we should anyway have something in the parser and with which 
exact wording (just tweak what I sent earlier replacing 'exactly one 
parenthesized expression' with 'exactly one element'?!?)


Thanks,
Paolo.

Re: [C++ Patch] PR 51911 V2 ("G++ accepts new auto { list }")

[Ville Voutilainen]

On 11 September 2015 at 23:05, Jason Merrill  wrote:
> Hmm, I think we really ought to accept
>
>   new auto { 2 }
>
> to be consistent with all the other recent changes to treat { elt } like
> (elt); this seems like a piece that was missed from DR 1467.  Do you agree,
> Ville?


Yes. I thought we already accept it.

Re: [C++ Patch] PR 51911 V2 ("G++ accepts new auto { list }")

[Jason Merrill]

On 09/11/2015 03:11 PM, Paolo Carlini wrote:

this is a slightly reworked (simplified) version of a patch I sent a
while ago. The issue is that we are not enforcing at all 5.3.4/2 in the
parser, thus we end up rejecting the first test below with a misleading
error message talking about list-initialization (and a wrong location),
because we diagnose it too late like 'auto foo{3, 4, 5};', and simply
accepting the second. Tested x86_64-linux.


Hmm, I think we really ought to accept

  new auto { 2 }

to be consistent with all the other recent changes to treat { elt } like 
(elt); this seems like a piece that was missed from DR 1467.  Do you 
agree, Ville?


Jason