Re: template argument required

[Larry I Smith]

Patrick Rammelt wrote:
> Hi
>
> I have just upgraded from gcc-3.3.3 to gcc-4.0.0 Trying to compile some
> old code I stumbled over an error. I created this short example:
>
> -------------------- gcctest.cpp -----------------------------
> #include <iostream>
>
> using namespace ::std;
>
> template <class T>
> class A {
> public:
>
>   A (void) {}
>
>   template <class X>
>   class A& foo (X p) {         // no error without "class"
>     cout << "template foo\n";
>     return(*this);
>   }
>
> };
>
> int main (void) {
>
>   A<double> a1, a2;
>   a1.foo(a2);                  // line 22: error (see below)
>
>   exit(0);
> }
> --------------------------------------------------------------------
>
> no errors when compiling it with g++-3.3.3, but g++-4.0.0 (and 
> g++-3.4.1) complaints:
>
> gcctest.cpp: In function ‘int main()’:
> gcctest.cpp:22: error: template argument required for ‘struct A’
> gcctest.cpp:22: error: no matching function for call to
>                 ‘A<double>::foo(A<double>&)’
>
> Substituting "class A&" by just "A&" in foo it compiles without any 
> warnings or errors (and works as expected). Does this make any sense, or 
> is it a bug?
>
> Thanks and ciao,
> Patrick

The definition of foo() is ambiguous.
Does this fix it?

   template <class X>
   class A<T> & foo (X p) {         // <-- specify WHICH type of 'A'
     cout << "template foo\n";
     return(*this);
   }

Regards,
Larry

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