Re: [boost] [optional]none.hpp causes VC7.1 precompiled header to behave erratically

From: Gennaro Prota (gennaro_prota_at_[hidden])
Date: 2006-07-16 05:45:04

On Sun, 16 Jul 2006 01:16:10 -0400, "Sean Huang"
<huangsean_at_[hidden]> wrote:

>Interestingly, I notice that boost::none is defined in an unnamed namespace. 

That really surprised me. As a rule of thumb unnamed namespaces
shouldn't be used in headers. In the rare cases where a good reason
exists for doing the contrary, that should be adequately commented.

>Since boost::none is const and thus has internal linkage so I removed the 
>unnamed namespace and everything started working again. So my questions is 
>what purpose the unnamed namespace serves? Can it be removed in light of 
>this problem with precompiled headers?

If there are good reasons for having it, it should be removed
regardless of the precompiled header problem. An unnamed namespace has
a name which is unique to its translation unit, not source file.

I'm also surprised that both none.hpp and none_t.hpp are in the boost
root dir. Do they have any general usage that justifies that? (I think
I was guilty of a similar sin with non_type.hpp and I'd be happy to
move it)

--
[ Gennaro Prota, C++ developer for hire ]
[    resume:  available on request      ]