Patchwork [C++,/,RFC] PR 53211

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Submitter Paolo Carlini
Date June 18, 2013, 12:21 a.m.
Message ID <51BFA813.9060100@oracle.com>
Download mbox | patch
Permalink /patch/252072/
State New
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Comments

Paolo Carlini - June 18, 2013, 12:21 a.m.
Hi,

On 06/17/2013 10:30 PM, Jason Merrill wrote:
> On 06/17/2013 04:08 PM, Paolo Carlini wrote:
>> +      if (TREE_CODE (TREE_TYPE (*tp)) == ARRAY_TYPE
>> +      && !TYPE_DOMAIN (TREE_TYPE (*tp))
>> +      && DECL_INITIAL (*tp)
>> +      && type_dependent_expression_p (DECL_INITIAL (*tp)))
>> +    return *tp;
>
> I think this approach makes sense, but it should go in 
> type_dependent_expression_p rather than instantiation_dependent_r.
>
> And please revert my fix for 56794, since this should fix one as well.
I see... There is a little difficulty in that 56794 involves a non-type 
variadic parameter and in that case type_dependent_expression_p returns 
false. If I use value_dependent_expression_p things work, but I'm not 
sure it's 100% correct.

I considered replacing it with uses_template_parms?!? Testing is fine 
with it too. It's also fine with both type_dependent_expression_p || 
value_dependent_expression_p.

Eventually, we'll have to decide where we want to commit this: 56794 is 
fixed in 4.7 and 4.8 too, but it's true that the issue with the specific 
testcase attached by Jon isn't a regression.

Thanks,
Paolo.

////////////////
/cp
2013-06-18

	PR c++/53211
	* pt.c (type_dependent_expression_p): Handle an array of unknown
	bound depending on a variadic parameter.
	* parser.c (cp_parser_range_for): Revert PR56794 changes.

/testsuite
2013-06-18

	PR c++/53211
	* g++.dg/cpp0x/decltype55.C: New.
Jason Merrill - June 18, 2013, 2:15 p.m.
On 06/17/2013 08:21 PM, Paolo Carlini wrote:
> I see... There is a little difficulty in that 56794 involves a non-type
> variadic parameter and in that case type_dependent_expression_p returns
> false. If I use value_dependent_expression_p things work, but I'm not
> sure it's 100% correct.

I don't think we need to consider whether the initializer is dependent 
here; if the array has no length and has an initializer, it must be that 
we couldn't determine its length in cp_complete_array_type because it is 
dependent.

> Eventually, we'll have to decide where we want to commit this: 56794 is
> fixed in 4.7 and 4.8 too, but it's true that the issue with the specific
> testcase attached by Jon isn't a regression.

I think apply it to 4.8 as well.

Jason

Patch

Index: cp/parser.c
===================================================================
--- cp/parser.c	(revision 200151)
+++ cp/parser.c	(working copy)
@@ -9750,10 +9750,7 @@  cp_parser_range_for (cp_parser *parser, tree scope
 	range_expr = error_mark_node;
       stmt = begin_range_for_stmt (scope, init);
       finish_range_for_decl (stmt, range_decl, range_expr);
-      if (range_expr != error_mark_node
-	  && !type_dependent_expression_p (range_expr)
-	  /* The length of an array might be dependent.  */
-	  && COMPLETE_TYPE_P (complete_type (TREE_TYPE (range_expr)))
+      if (!type_dependent_expression_p (range_expr)
 	  /* do_auto_deduction doesn't mess with template init-lists.  */
 	  && !BRACE_ENCLOSED_INITIALIZER_P (range_expr))
 	do_range_for_auto_deduction (range_decl, range_expr);
Index: cp/pt.c
===================================================================
--- cp/pt.c	(revision 200151)
+++ cp/pt.c	(working copy)
@@ -20079,6 +20079,26 @@  type_dependent_expression_p (tree expression)
       && VAR_HAD_UNKNOWN_BOUND (expression))
     return true;
 
+  /* An array of unknown bound depending on a variadic parameter, eg:
+
+     template<typename... Args>
+       void foo (Args... args)
+       {
+         int arr[] = { args... };
+       }
+
+     template<int... vals>
+       void bar ()
+       {
+         int arr[] = { vals... };
+       }  */
+  if (VAR_P (expression)
+      && TREE_CODE (TREE_TYPE (expression)) == ARRAY_TYPE
+      && !TYPE_DOMAIN (TREE_TYPE (expression))
+      && DECL_INITIAL (expression)
+      && value_dependent_expression_p (DECL_INITIAL (expression)))
+   return true;
+
   if (TREE_TYPE (expression) == unknown_type_node)
     {
       if (TREE_CODE (expression) == ADDR_EXPR)
Index: testsuite/g++.dg/cpp0x/decltype55.C
===================================================================
--- testsuite/g++.dg/cpp0x/decltype55.C	(revision 0)
+++ testsuite/g++.dg/cpp0x/decltype55.C	(working copy)
@@ -0,0 +1,20 @@ 
+// PR c++/53211
+// { dg-do compile { target c++11 } }
+
+template<typename A, typename B>
+  struct is_same { static const bool value = false; };
+
+template<typename A>
+  struct is_same<A, A> { static const bool value = true; };
+
+template<typename... Args>
+void func(Args... args)
+{
+  int arr[] = { args... };
+  static_assert (is_same<decltype(arr), int[sizeof...(Args)]>::value, "");
+}
+
+int main()
+{
+  func(1, 2, 3, 4);
+}