Re: Re: [boost] Next revision of boost::thread

From: William E. Kempf (wekempf_at_[hidden])
Date: 2003-01-09 06:51:41

> From: Beman Dawes <bdawes_at_[hidden]>
> At 05:17 PM 1/8/2003, William E. Kempf wrote:
>  >> From: Rene Rivera <grafik666_at_[hidden]>
>  >> I rather dislike the conditional compilation solution. It makes it 
> rather
>  >> harder to write portable code as it makes for doing conditional PP code
>  >> outside of the library. Would it not be preferable to throw some form 
> of
>  >> "unimplemented"/"unsupported" exception? Another option would be a
>  >discovery
>  >> interface to find out what's supported in the platform. Such a 
> discovery
>  >> interface could be used with MPL to get the equivalent of PP.
>  >
>  >Note that we do throw exceptions in many cases where things aren't
>  >supported.  However, if a large category of functionality is not 
> available,
>  >such as scheduling, there's reasons to prefer conditional compilation.
>  >First, you can get rid of unecessary code.  Second, you know from 
> attempts
>  >to compile whether or not code can actually be ported to a given 
> platform.
>  >IOW, the exception approach is only useful when you can compensate for 
> the
>  >lack of a feature at run time.
> 
> I'm not a fan of conditional compilation either.
> 
> I'd rather see the functions always supplied, even as stubs, unless it is 
> absolutely sure that every use represents a serious error.
> 
> For example, setting the stack size may have no effect on some platforms, 
> but why should it be considered an error?
> 
> There could be a compile time way to tell if the feature has any effect, so 
> if the user wishes to tailor the code, it is possible to do so.
> 
> Particularly between major platforms like POSIX and Windows, I'd hope that 
> programs could be moved back and forth without user code being concerned 
> about presence or absence of features.

That's the rub, though.  Some features are killer for portability when an application must maintain "realtime constraints".  If a platform doesn't support the features you need for realtime programming, you simply can't target that platform, and a stubbed approach is going to cause you more problems than it's going to help.

But I understand why people don't like conditional compilation... and that's precisely why I brought the subject up.  If there's a solution I'm not thinking of, I'd prefer to have another approach as well.

William E. Kempf
wekempf_at_[hidden]