[boost] [for Win] [was: Re: 1.30.0->1.30.2: no more thread support for Linux?]

From: vc (vcotirlea_at_[hidden])
Date: 2003-09-01 04:32:06

Hi,

I haven't followed this thread completely, but I have a question.
I'm working on Win 2k, and I'm using VC++ 7.1. Building
boost with this toolset, do I need to specify something to make it
thread-safe?

TIA,
Viv

----- Original Message -----
From: "John Maddock" <boost.regex_at_[hidden]>
To: "Boost mailing list" <boost_at_[hidden]>
Sent: Sunday, August 31, 2003 12:33 PM
Subject: Re: [boost] Re: 1.30.0->1.30.2: no more thread support for Linux?

> > > Threading support is on when BOOST_HAS_THREADS is defined, and off
when
> it's
> > > not, or forced off by defining BOOST_DISABLE_THREADS, you'll find both
> of
> > > these mentioned in the configure generated user.hpp (and in the config
> > > docs).
> >
> > So if I my program runs only on systems that I know support threads,
> > and I want shared_ptr to use threading support, my program can guarantee
> > this by defining BOOST_HAS_THREADS? No matter whether the user's Boost
> > install is -
> >
> > 1) Simply extracted from the tarball
> > 2) Configured without thread support
> > 3) Configured with thread support
> >
> > And I don't need to define anything about the platform thread library
> being
> > used, like BOOST_HAS_PTHREADS?
>
> OK lets start with Linux and gcc as a specific and special case - in this
> case I think that will work - BOOST_HAS_PTHREADS will be defined anyway,
but
> remember that your std lib will not be thread safe unless you define
> _REENTRANT, and if you do that then BOOST_HAS_THREADS will get defined
> anyway by the config system (either the out-the-box version or the
> configure'd one).  Of course the user could always manually configure
boost
> in some obscure way, or deliberately disable thread support with
> BOOST_DISABLE_THREADS, but if they've done that then you should probably
be
> emitting a #error not trying to work around it.
>
> In the general case though, we're back to the situation that your code
will
> not be thread safe unless you invoke your chosen compiler with some magic
> special flag (or in the case of IBM Visual Age use a different compiler
> front end altogether), and if you do that then Boost.config will detect
it's
> presence by whatever macros it sets (usually but not always _REENTRANT)
and
> turn on BOOST_HAS_THREADS.  You should always regard BOOST_HAS_THREADS as
> *information*, not as something you set yourself, in 99% of cases if you
> find it's not set, then it's because the compiler in it's current mode
isn't
> capable of producing thread safe code.
>
> Note for example that Boost.config explicitly defines
BOOST_DISABLE_THREADS
> for gcc on some platforms because we know that gcc isn't capable of
> producing thread safe code on those platforms yet (even though they do
have
> a perfectly good pthread lib).
>
> Finally if you're configuring your program via autoconf then there are
some
> nice looking autoconf macros on the net, for example:
> http://ac-archive.sourceforge.net/Installed_Packages/acx_pthread.html.
>
> Sorry to make this complicated, but threads _are_ complicated....
>
> John.
>
>
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