Re: VS 2005 Bug?

From:

"John Carson" <jcarson_n_o_sp_am_@netspace.net.au>

Newsgroups:

microsoft.public.vc.language

Date:

Tue, 13 Feb 2007 22:28:26 +1100

Message-ID:

<emhVJJ2THHA.1364@TK2MSFTNGP06.phx.gbl>

<uvts_cvs@yahoo.com> wrote in message
news:1171360780.845664.323990@m58g2000cwm.googlegroups.com

Hi everybody,
consider this little chunk of code:

void foo(int i=0) {return;}

template <typename f_t>
void call (f_t const &f)
{
  f (0);
}

int main ()
{
  call (foo);
  return 0;
}

compiling it I get the error C2383: 'f_t' : default-arguments are not
allowed on this symbol. Reading the documentation I see that microsoft
states that my code is breaking the standard, but I don't really think
so.
In fact passing foo to call we are istantiating the function call<void
(*)(int)>. Is this not true?
Therefore the compiler doesn't bother me if I substitute the line
"call(foo)" with call(static_cast<void(*)(int)>(foo)).

Comeau online compiler compliles it without giving the error. Do you
this code is really breaking the standard?

Looks like a bug. You aren't allowed to have default arguments on function
pointers, but foo is not a function pointer (though it is converted to one
when supplied as an argument to call), so the rule shouldn't affect foo.

The following is one workaround:

void foo(int i=0) {return;}
void (*pfoo)(int) = &foo;

template <typename f_t>
void call (f_t const &f)
{
   f (0);
}

int main ()
{
   call (pfoo);
   return 0;
}

--
John Carson