Re: Function pointers and default arguments

From:
 James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Sun, 05 Aug 2007 18:03:47 -0000
Message-ID:
<1186337027.570356.110150@q75g2000hsh.googlegroups.com>
On Aug 5, 2:13 am, Gianni Mariani <gi3nos...@mariani.ws> wrote:

James Kanze wrote:


    [Note that as far as I can tell, this comment has nothing to
    do with what preceding in the thread.]

Interesting; this code compiles in gcc but not on comeau or VC++ 2005.

int f( int p = 5 )
{
     return p;
}

template <typename T>
T F( T fp )
{
     return fp;
}

#include <iostream>

int main()
{
     std::cout << F( f )() << "\n";
}

Ok, so who is wrong, GCC or Comeau + VC++ ?


What operator<< is being called? The type of F(f) is "int (*)(
int )" (a "function" type is treated as a pointer to function
type when it is a function parameter). There's no such
operator<< in the standard, and there's no implicit conversion
from a function pointer to anything which has an operator<<, so
a priori, it shouldn't compile.

What does the output look like? Could it be that g++ is
(illegally) converting the function pointer to void*?

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