Re: [boost] static templates in BOOST

From: David Abrahams (dave_at_[hidden])
Date: 2005-07-06 12:46:31

Steve Clamage <Stephen.Clamage_at_[hidden]> writes:

> We recently corrected the way our compiler (Sun C++) handles static templates, 
> and ran into a problem with some BOOST code. More than 100 tests in the suite 
> depend on code like this:
>
> template <typename T>
> struct S
> {
>    void foo(int);
> };
>
> template<class T , class U>
> static                              // static template ...
> void smart_cast_reference(U& u)
> {}
>
> template <typename T>
> void S<T>::foo(int c)
> {
>    smart_cast_reference< T& >(c);  // used in global function
> }
>
> int main()
> {
>    S<int> s;
>    s.foo(1);
> }
>
> You can't use a static template in a global template function because it 
> violates the One-Definition Rule, among possibly other rules. I have found that 
> other compilers accept this code, but reject it when you put them in 
> standard-conformning mode. (To see the rejection with some compilers, you need 
> to build the executable.)
>
> How critical to BOOST is this style of coding? Could the static templates be 
> made global?

Steve,

It really surprises me to hear that we have lots of this; it isn't a
common idiom in Boost.  Could you point us to some of the files where
it's used?

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com