g++ template instantiation warnings?

g++ template instantiation warnings?

[Brendt Wohlberg]

Is there a a -W option, or some other method, of switching off the warnings:

warning: friend declaration `void swap(class A<T> &, class A<T> &)'
warning: will not be treated as a template instantiation
warning: unless you compile with -fguiding-decls
warning: or add <> after the function name

for friend declarations *without* turning them into template instantiations
(when compiling with -fno-implicit-templates, for example)?

--
 Brendt Wohlberg                       E-mail: brendt@dip.ee.uct.ac.za
 Department of Electrical Engineering  Phone : +27 21 650 3466
 University of Cape Town               Fax   : +27 21 650 3465

Re: g++ template instantiation warnings?

[Alexandre Oliva]

Brendt Wohlberg writes:

> warning: friend declaration `void swap(class A<T> &, class A<T> &)'
> warning: will not be treated as a template instantiation

> for friend declarations *without* turning them into template instantiations
> (when compiling with -fno-implicit-templates, for example)?

In fact, the error message has nothing to do with actually generating
code for template instantiations, it has to do with compiling that
declaration as referring to a template function specialization or a
non-template function.  If you don't add angle brackets, you won't be
referring to a template specialization:

void foo(int);
template <typename T> void foo(T);

class bar {
  friend void foo(int);   // refers to the non-template version
  friend void foo<>(int); // refers to the template specialization
};

Maybe the error message should be changed to say `template
specialization' instead of `template instantiation'.

-- 
Alexandre Oliva
mailto:oliva@dcc.unicamp.br mailto:aoliva@acm.org
http://www.dcc.unicamp.br/~oliva
Universidade Estadual de Campinas, SP, Brasil