Re: PR c++/34758 Bad diagnostic for circular dependency in constructor default argument

[Manuel López-Ibáñez <lopezibanez at gmail dot com>]

Bootstrapped and regression tested on x86_64-unknown-linux-gnu with
--enable-languages=all,ada

OK for trunk?

2009-02-11  Manuel Lopez-Ibanez  <manu@gcc.gnu.org>

	PR c++/34758
cp/
	* call.c (convert_default_argument): Clarify error message.
testsuite/
	* g++.dg/parse/pr34758.C: New.



2009/2/9 Mark Mitchell <mark@codesourcery.com>:
> Manuel López-Ibáñez wrote:
>
>>> Why is it worth having two messages?  The people reading the messages
>>> are programmers; they'll understand that saying "argument 1" for a
>>> 1-argument function is just a computer being a bit redundant.
>>
>> I do not have the particular mail discussion at hand, but this was
>> explicitly requested there. I think it is nice, and I already took
>> that trouble to implement it. But if it is such a problem, then I
>> guess it can be de-implemented.
>
> I think it's overkill.
>
>> I do not see that convert_for_initialization documents parmnum
>> anywhere. The 0-based was already there, I haven't changed it.
>>
>> BTW, convert_for_initialization uses %P to print parmnum, whereas the
>> original code in convert_default_arg is using %d, so that may be the
>> reason why it does not use parmnum+1.
>
> OK, so then lets use %P in both places.
>
> Thanks,
>
> --
> Mark Mitchell
> CodeSourcery
> mark@codesourcery.com
> (650) 331-3385 x713
>

Index: gcc/testsuite/g++.dg/parse/pr34758.C
===================================================================
--- gcc/testsuite/g++.dg/parse/pr34758.C	(revision 0)
+++ gcc/testsuite/g++.dg/parse/pr34758.C	(revision 0)
@@ -0,0 +1,29 @@
+// PR 34758 Bad diagnostic for circular dependency in constructor default argument
+// { dg-do compile }
+// { dg-options "" }
+struct A
+{
+  A (const A& = A()); // { dg-error "'\[^\n\]*A::A\[^\n\]*' needs to be declared before called with a default argument" }
+};
+
+
+struct S {
+  S(const S& = f()); // { dg-error "'\[^\n\]*S::f\[^\n\]*' needs to be declared before called with a default argument" }
+  static const S& f(int i = 3);
+};
+
+struct J {
+  J(const J& = f(2)); // { dg-error "'\[^\n\]*J::f\[^\n\]*' needs to be declared before called with a default argument for parameter 2" }
+  static const J& f(int i = 3, int j = 4);
+};
+
+struct Z {
+  Z(const Z& = f(4));
+  static const Z& f(int i = 3);
+};
+
+struct X {
+  X(const X& = g());
+  static const X& g(void);
+};
+
Index: gcc/cp/call.c
===================================================================
--- gcc/cp/call.c	(revision 143971)
+++ gcc/cp/call.c	(working copy)
@@ -4921,12 +4921,13 @@ cxx_type_promotes_to (tree type)
 
   return promote;
 }
 
 /* ARG is a default argument expression being passed to a parameter of
-   the indicated TYPE, which is a parameter to FN.  Do any required
-   conversions.  Return the converted value.  */
+   the indicated TYPE, which is a parameter to FN.  PARMNUM is the
+   zero-based argument number.  Do any required conversions.  Return
+   the converted value.  */
 
 static GTY(()) VEC(tree,gc) *default_arg_context;
 
 tree
 convert_default_arg (tree type, tree arg, tree fn, int parmnum)
@@ -4936,13 +4937,12 @@ convert_default_arg (tree type, tree arg
 
   /* If the ARG is an unparsed default argument expression, the
      conversion cannot be performed.  */
   if (TREE_CODE (arg) == DEFAULT_ARG)
     {
-      error ("the default argument for parameter %d of %qD has "
-	     "not yet been parsed",
-	     parmnum, fn);
+      error ("%qD needs to be declared before called with a default argument "
+	     "for parameter %P", fn, parmnum);
       return error_mark_node;
     }
 
   /* Detect recursion.  */
   for (i = 0; VEC_iterate (tree, default_arg_context, i, t); ++i)