[boost] Re: [filesystem] Can't compile on Tru64/gcc

From: Beman Dawes (bdawes_at_[hidden])
Date: 2005-04-04 19:51:30

"Jonathan Wakely" <cow_at_[hidden]> wrote in message 
news:20050404134320.GA88664_at_compsoc.man.ac.uk...

> Out of interest, why can't you just use _SC_THREAD_SAFE_FUNCTIONS if it's
> defined?
>
> Also, if _POSIX_THREAD_SAFE_FUNCTIONS == 0, I thought that meant *not*
> supported (in which case sysconf() would return -1) ?  Does the test have
> to be >= not just > ?
>
> I'd have written it:
>
> #     if defined(_SC_THREAD_SAFE_FUNCTIONS)
>      if ( ::sysconf( _SC_THREAD_SAFE_FUNCTIONS ) > 0 )
>        { return ::readdir_r( dirp, entry, result ); }
> #     endif
>
> But I didn't realise this wasn't good enough  :-|

This is the first time I've ever used the POSIX config mechanisms, so I may 
have it wrong. I'll check... Hum... I find the POSIX docs for sysconf() 
pretty impeneratable regarding the return value. I can see why I took >=0 to 
be needed, but I could also read it in a way that >0 would be OK.

Any POSIX experts out there?

> Finally, readdir_r() is available on FreeBSD even though neither
> _POSIX_THREAD_SAFE_FUNCTIONS not _SC_THREAD_SAFE_FUNCTIONS is defined.
> I don't know how to test for it though, FreeBSD's sysconf() only claims
> to support POSIX 1990, even though some later interfaces are available.

Someone with access to that system needs to figure out what PP macro to look 
for.

Thanks,

--Beman