From: williamkempf_at_[hidden]
Date: 2001-09-24 15:21:56
--- In boost_at_y..., Darin Adler <darin_at_b...> wrote:
> on 9/24/01 1:04 PM, williamkempf_at_h... at williamkempf_at_h...
> wrote:
>
> > Sorry, I didn't write this stuff and didn't look close enough ;).
> > However, I think it's still correct as is. I *believe* that
certain
> > compilers always have threading support "turned on" (gcc is one
such
> > compiler, isn't it?), and so the compiler portion of the config
> > system defines BOOST_HAS_THREADS. Since none of the "magic
macros"
> > in the first section will exist in this case BOOST_HAS_THREADS is
> > never redefined. The !defined(BOOST_DISABLE_THREADS) in the first
> > portion is superflous because of the second portion, but it's not
> > really incorrect. I'd say you could safely remove it in the first
> > portion if it causes confusion, but it's technically still
correct as
> > is.
>
> Yes.
>
> But many preprocessors warn if you define a macro twice. So we
might need to
> add a !defined(BOOST_HAS_THREADS) to that expression since
BOOST_HAS_THREADS
> might already be defined.
It should be defined *ONLY* if the compiler does not support the
concept of having thread support enabled and disabled, such as for
gcc. So there's no need to check !defined(BOOST_HAS_THREADS) because
the other checks already preclude this from being defined. In fact,
you could argue that we want a warning if this isn't the case to help
us insure that BOOST_HAS_THREADS is not defined by compiler/platform
config information if the compiler supports detection through the
various "magic macros" such as _MT, et. al.
Bill Kempf