Template specialization error

Template specialization error

[Mark Norman]

Hi,

I'm trying to port some code to work on gcc.  Unfortunately I have
come across an error which I have been unable to solve.  I have
created a small example program which illustrates the compiler error I
get.

Compiling the following code using gcc 3.3.4 or 3.4.3 gives the following error:
test.C: In instantiation of `Bar<void>':
test.C:31:   instantiated from here
test.C:7: error: forming reference to void

When calling "fun<void>( k )" it appears that g++ gets confused with
the last argument in template  3 (see code) even though it should be
using the void specialization in Template 2.



template<class T>
struct Foo;

template<class T>
struct Bar
{
  typedef Foo< const T& > fooTypedef;
};

// Template 1
template <class T>
T fun( int Key )
{ };
  
// Template 2
// Specialization of fun template for void.
template <> inline 
void fun<void>( int Key ) { };

// Template 3
// The following function causes the error.  If you remove/rename this function
// or replace "typename Bar<T>::fooTypedef" with "Foo< const T& >"
// it compiles ok.
template <class T>
T fun( int Key, const typename Bar<T>::fooTypedef& theFoo )
{ };


int main()
{
  int k;

  fun<char>( k );
  fun<void>( k );
}


Am I doing something incorrectly here?

Thanks for any help you can provide.

Mark

Re: Template specialization error

[corey taylor]

Mark,

This may help.  Section 14.1 paragraph 7

A non-type template-parameter shall not be declared to have floating
point, class, or void type. [Example:
template<double d> class X; // error
template<double* pd> class Y; // OK
template<double& rd> class Z; // OK
—end example]

corey

On 5/30/05, Mark Norman <mpnorman@gmail.com> wrote:
> Hi,
> 
> I'm trying to port some code to work on gcc.  Unfortunately I have
> come across an error which I have been unable to solve.  I have
> created a small example program which illustrates the compiler error I
> get.
> 
> Compiling the following code using gcc 3.3.4 or 3.4.3 gives the following error:
> test.C: In instantiation of `Bar<void>':
> test.C:31:   instantiated from here
> test.C:7: error: forming reference to void
> 
> When calling "fun<void>( k )" it appears that g++ gets confused with
> the last argument in template  3 (see code) even though it should be
> using the void specialization in Template 2.
> 
> 
> 
> template<class T>
> struct Foo;
> 
> template<class T>
> struct Bar
> {
>   typedef Foo< const T& > fooTypedef;
> };
> 
> // Template 1
> template <class T>
> T fun( int Key )
> { };
> 
> // Template 2
> // Specialization of fun template for void.
> template <> inline
> void fun<void>( int Key ) { };
> 
> // Template 3
> // The following function causes the error.  If you remove/rename this function
> // or replace "typename Bar<T>::fooTypedef" with "Foo< const T& >"
> // it compiles ok.
> template <class T>
> T fun( int Key, const typename Bar<T>::fooTypedef& theFoo )
> { };
> 
> 
> int main()
> {
>   int k;
> 
>   fun<char>( k );
>   fun<void>( k );
> }
> 
> 
> Am I doing something incorrectly here?
> 
> Thanks for any help you can provide.
> 
> Mark
>