Re: [boost] [system] Header-only Boost.System by default ?

Subject: Re: [boost] [system] Header-only Boost.System by default ?
From: Groke, Paul (paul.groke_at_[hidden])
Date: 2017-10-10 08:21:12

> -----Original Message-----
> From: Boost [mailto:boost-bounces_at_[hidden]] On Behalf Of Andrey
> Semashev via Boost
> Sent: Dienstag, 10. Oktober 2017 09:32
> Subject: Re: [boost] [system] Header-only Boost.System by default ?
> 
> It will have the same address as long as get_basic_error_category() is called
> within the same module (dll, so, exe, etc.) If this function is compiled in
> different modules then there will be multiple instances of the category with
> different addresses.
> 
> On Linux and probably other Unix-like systems this can be solved by
> exporting the category instance, which is the default. I don't think this can be
> done on Windows - you'd have to export get_basic_error_category for that
> instead and it will make this code less friendly to header-only libraries.

And even if the "same address" thing was solvable (which I think it is, although not pretty and it would require interface changes), there is the problem with unloading DLLs/SOs. You'd have to pin every module that contains error categories. Which IMO is a side effect that you really don't expect and want, especially from a header-only library.

Paul Groke