Re: [boost] [swap] End-user allowed to add overloads to boost namespace?

From: David Abrahams (dave_at_[hidden])
Date: 2008-07-26 12:30:50

on Sat Jul 26 2008, Steven Watanabe <watanabesj-AT-gmail.com> wrote:

> AMDG
>
> Niels Dekker - mail address until 2008-12-31 wrote:
>> Once the boost::swap utility would be used by other Boost libraries, end
>> users might want to add a custom overload of swap for their classes to
>> the boost namespace.  Especially when users would have to deal with
>> lacking ADL support of their compiler. Would it be okay for them to do
>> so?  Or are there some moral objections, or technical issues, regarding
>> a user-provided overload within the boost namespace?
>>   
>
> Adding overloads to namespace boost is not guaranteed to work either.
>
> template<class T>
> void foo(T& t1, T&t2) {
>    boost::swap(t1, t2);
> }
>
> class X {};
>
> namespace boost {
>    void swap(X&, X&); // not found by foo.
> }

Well, not by a conforming compiler.  Niels is talking about compilers
with bugs, though.  I don't know if this would be a possible workaround
for any of those compilers or not, but several compilers do all name
lookup in phase 2 so this stands a chance of working.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com