Re: [Boost-build] [Patch] Fix Python support on Darwin

From: Vladimir Prus (ghost_at_[hidden])
Date: 2006-09-24 03:13:52

On Friday 22 September 2006 22:28, Doug Gregor wrote:
> We ran into some linking issues on Mac OS X with the Python library.
> This patch below *seems* to fix the issue, because the Darwin linker
> fails if there are undefined symbols (usually supplied by the Python
> library) when linking libboost_python-whatever.dylib. 

You mean, a shared library can't have undefined symbols? This so Windows-like, 
they must have hacked ld to get this behaviour.

> The only ways 
> to force the linker to ignore those undefined symbols involve -
> flat_namespace, which Apple quitely broken in the latest release.
>
> In any case, the change is just to link against the Python libraries
> with -framework Python. On other *nix variants, this would be bad,
> because we'd end up with two copies of the Python symbols... one
> linked into the libboost_python library and the other provided by the
> Python interpreter. 

Only if Python lib is static, which unfortunately is the case on half the 
systems ;-)

> On Mac OS X, I believe frameworking linking is 
> always dynamic linking, so the problem doesn't crop up. At least, the
> Python tests seem to be running...
>
> I still don't think we're handling extension modules properly. We
> should be linking them with -bundle and (possibly) -bundle_loader,
> but we aren't. Darwin is such a pain :(

What's the difference between -framework and -bundle? 

In any way, I know too little about Darwin to make any meaningfull comments. 
I'd suggest to go ahead with this patch. If somebody has more comments we can 
always adjust things.

> --- /u/dgregor/Projects/boost-1.34.0/tools/build/v2/tools/
> python.jam    2006-09-21 10:54:35.000000000 -0400
> +++ python.jam  2006-09-22 11:29:20.000000000 -0400
> @@ -363,19 +363,15 @@
>       }
>       PYTHON_FRAMEWORK = $(PYTHON_FRAMEWORK:D)/Python ;
> -    alias python_for_extensions
> -      :
> -      :
> -      :
> -      : <include>$(includes)
> -      ;
> -
>       alias python
>
>         : <os>MACOSX <toolset>darwin
>         :
>         : <include>$(includes) <framework>$(PYTHON_FRAMEWORK)
>
>         ;
> +
> +    .alias-defined = true ;
> +    alias python_for_extensions : python ;

But can you please add a comment here? At least, saying that on Darwin, 
extensions must link to Python directly, or link error will occur?

Thanks,
Volodya

> }
> rule init-nt ( version : root ? : includes ? : libraries ? : cygwin-
> condition ? )
>
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-- 
Vladimir Prus
http://vladimir_prus.blogspot.com
Boost.Build V2: http://boost.org/boost-build2