On Thu, May 13, 2004 at 01:22:13PM +0400, Vladimir Prus wrote:
So, for single threaded builds 1. Boost will think it's MT build and call pthread_* functions. 2. Toolset won't add '-pthread' to linker command line
Bottom like: you'll get link failures for single-thread builds.
We can fix that: we already have platforms/toolsets where the default, in fact the *only* behaviour is for builds to be thread safe, even if you specify <threading>single.
I really don't think we want to disable <threading>signle for such a popular platform.
That's why we need G++ to define something whenever -pthread is given on the command line. There's currently nothing suitable in GCC 3.4. Ideally it would be defined for all platforms, since x86-linux isn't the only non-windows system :) Some platforms (e.g. NetBSD) automatically define _PTHREADS when -pthread is given. It might be possible to do that for all systems. But there might be good reasons not to.
I think the problem here is that we have two options for the <threading> variant, but really we should have three:
1) threading must be on 2) threading must be off 3) whatever the default is for the compiler
Most people actually want option (3) a lot of the time,
Actually, I just don't want to pay for MT, unless I really mean to use the code in MT environment.
I understand (3) to mean MT when -pthread is given, single otherwise.
and currently that's what <threading>single more or less gives you, ideally though we would map builds for option 3 to either 1 or 2 so we don't build libraries we've actually already built.
I don't really understand the problem. For example, are there any compilers which generate MT code by default? And, what's "default for the compiler"?
The problem is that boost (currently) assumes you're compiling a MT app if you use GCC 3.4, so the preprocessed output refers to the pthread_* functions (which means G++ 3.4 _with_boost_ compiles MT by default) which then causes linker errors if you didn't use -pthread. If you manually define BOOST_DISABLE_THREADS then Boost doesn't refer to the pthread_* functions and you don't need to give -pthread. jon -- "A foolish consistency is the hobgoblin of little minds..." - Ralph Waldo Emerson