[fpc-devel] (hack) calling fpc libraries from other languages on freebsd/amd64

[Sergei Gorelkin]

21.11.2013 0:45, Michal Wallace пишет:
> Hey all.
>
> I had a problem and I fixed it in the compiler, but I'm not sure
> what the ramifications of my fix are for other people.
>
> My goal was to expose some pascal code to python, as per:
>
> http://wiki.freepascal.org/Developing_Python_Modules_with_Pascal
>
> This works fine for me on windows but failed on freebsd/amd64.
>
> When I would try to load my shared library as a python module, it would fail, saying: "Undefined
> Symbol: operatingsystem_parameter_envp"
>
> This issue was reported by someone else but it was (mistakenly?) marked as a duplicate issue and closed:
>
> http://bugs.freepascal.org/view.php?id=15422
>
> Anyway, the problem appears to be in this file:
>
> http://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/rtl/freebsd/x86_64/dllprt0.as?revision=25737&view=markup
>
> It has the comment:
>
> # FreeBSD RunTime dynamic loader only
> # calls the functions specified by -init
> # as functions without parameters
> # Thus, it is not possible to retrieve argc, argv and envp
> 	# On x86_64 CPU, using weak for the operatingsystem_parameter_XXX
>
> 	# allows to bind to main program parameters,
>
> # but this does not seem to work for i386 loader.
>
> Then at the bottom:
>
> /* Do not fail linkage if argc, argv and envp are not found. */
> .weak operatingsystem_parameter_argc
> .weak operatingsystem_parameter_argv
> .weak operatingsystem_parameter_envp
>
> My change was to comment these lines out and copy the lines from prt0.as <http://prt0.as> :
> 	
>
>
> .global operatingsystem_parameter_envp
> .global operatingsystem_parameter_argc
> .global operatingsystem_parameter_argv
> .set operatingsystem_parameter_envp,operatingsystem_parameters+0
> .set operatingsystem_parameter_envp,operatingsystem_parameters+0
> .set operatingsystem_parameter_envp,operatingsystem_parameters+0
>
> Then after recompiling fpc, I was able to compile a *.so file usable from python.
>
> But... It seems like the original .weak version was done quite deliberately, so I suspect that if I
> submit a patch, it would break
> things for other people. OTOH, I'd like to get a fix for my issue
> into trunk.
>
> What should I do?
>

Studying sources of FreeBSD dynamic loader reveals that, although it does not pass argc, argv and 
envp to the initialization function in .init section, it *does* pass them to procedures pointed to 
from .init_array section. Generally, .init_array is considered as a replacement for .init. 
Therefore, the correct solution would be to change initialization to use .init_array and remove all 
associated hacks.

Regards,
Sergei