Re: [Pyobjc-dev] Re: libffi

[Jack J. <Jac...@cw...>]

On Friday, Nov 8, 2002, at 16:10 Europe/Amsterdam, Ronald Oussoren 
wrote:

> I got my copy from the GCC CVS some time ago. I checked out the CVS 
> HEAD and used just the libffi part. The only thing I had to do was a 
> small patch to configure: I kept complaining about a file in .., which 
> probably wasn't there because I didn't build the rest of GCC.
>
> As I said, I couldn't get it to build into a shared library. This 
> seems to be caused by an assembler file that is used for closures. 
> Just removing this file is of no use because I actually want to use 
> that feature.

I had a go at it, and by adding a "-read_only_relocs warning" argument 
to the link call that creates the dylib I managed to get it to work. 
So, I built a static libffi.a, linked that into a dynamic library 
(testffi.dylib, in my case) with the -read_only_relocs warning option, 
and linked against that library with a test program (without any funny 
options). That worked fine.

The ld man page states that relocation in readonly segments of shared 
libraries is something to be avoided, as the readonly segment will have 
to be copied and hence no longer can be shared. But, it is only to be 
*avoided*, it is implemented.

And if that doesn't work we should try to fix darwin_closure.S. Without 
known any PowerPC assembler (i.e. this paragraph should be considered 
as near-zero-content:-) my first guess is that the jump table at .L60 
is the problem. Either the table itself (although the .L44-.L60 form of 
the entries should have removed any relocation) or the loading of its 
address, a few lines above. Examining how the C compiler creates code 
for switch statements if -dynamic is in effect should give us a clue.

If we decide to use this I would suggest putting a copy of the code in 
the PyObjC source tree. The license seems to permit this, it appears to 
be a very liberal open source license (someone want to check this, 
please?). And as libffi isn't distributed at the moment the only 
alternative would be to point people at the gcc CVS tree, which isn't 
really for the faint of heart.
--
- Jack Jansen        <Jac...@or...>        
http://www.cwi.nl/~jack -
- If I can't dance I don't want to be part of your revolution -- Emma 
Goldman -