store pointer to template function?

[Suzanne Vogel]

Is it possible to store a pointer to a template function whose template
type is not known until runtime?

eg,
Can I store a pointer to this?

template<class T> f() {...}

I know how to store pointers to ordinary functions, but not template
functions.

Thanks,
Suzanne

 

[Jonathan Turkanis]

Is it possible to store a pointer to a template function whose template
type is not known until runtime?

eg,
Can I store a pointer to this?

template<class T> f() {...}

Unfortunately, no. You can store pointers to specializations of
template functions, but not the actual template. If you give an
example of your intended use, perhaps we can suggest another way to
accomplish the same thing.

I know how to store pointers to ordinary functions, but not template
functions.

They're stored just like other function pointer. You have to be
careful about getting the address of the correct overload.

Jonathan

 

[Ron Natalie]

Is it possible to store a pointer to a template function whose template
type is not known until runtime?

eg,
Can I store a pointer to this?

template<class T> f() {...}

No. Templates are instantiated at build time.
You can only get pointers to specific specializations.

 

[Gianni Mariani]

No. Templates are instantiated at build time.
You can only get pointers to specific specializations.

Except in this case, the function signature is independant of the
template argument. (and the syntax is incorrect too - but that's a
different issue)

This works:
(assuming the template function returns an int)

int (* ptr_fooFunc)() = &f<x>;

 

[Ron Natalie]

Except in this case, the function signature is independant of the
template argument. (and the syntax is incorrect too - but that's a
different issue)

It's still the case. There's no requirement that the function signature reflect the template
args. (Except for bugs in certain compilers like VC++ 6). It just means you have to
provide the explicit template argument list.

This works:
(assuming the template function returns an int)

int (* ptr_fooFunc)() = &f<x>;

Doesn't solve the problem the original poster asked for. They wanted to bind the function
by pointer later to a specific specialization. This binds it to the f<x> specialization at initialization
time.

 

[Suzanne Vogel]

Doesn't solve the problem the original poster asked for. They wanted to bind the function
by pointer later to a specific specialization. This binds it to the f<x> specialization at initialization
time.

Correct: doesn't solve the problem. Thanks, Ron. And thanks Gianni, for
the suggestion.

Suzanne