Re: Problem with Fortran shared libraries on OSX/Darwin

[Peter O'Gorman]

Tim Jenness wrote:

> On Fri, 3 Sep 2004, Peter O'Gorman wrote:
>
>
> > I don't believe that you'll get working executables this way.
>
>
> Except it all works fine. I'm not building executables with that patch,
> I'm just building the libraries. Executables include their own libgcc.a
> during the link phase. With the above patch I can build shared libraries
> that can link into exectuables (this is with 3 million lines of fortran so
> it's not a small project). Saying that, I'm happy to find out that I was
> fluking a fix that wasn't correct.
>
> I note that g++ seems to have the -nostdlib option for darwin 
> though (that's what gave me the idea).
>
>
> > The problem is actually the -single_module flag. It is needed to make c++ 
> > static constructors work better on darwin up to 7.x. The reason it fails on 
> > g77 (and on fsf gcc actually) is that Apple's gcc uses __private_extern__ 
> > symbols in libgcc and libstdc++. __private_extern__ symbols are magic, they 
> > are available in the static archive to resolve undefined symbols until they 
> > are linked whereupon they turn into local symbols. Fink's f77 libs don't 
> > have that magic.
>
>
> Thanks.
>
>
> > Anyway, I'll fix the darwin commands to work with fsf gcc before 
> > libtool-2.0. Thanks for the report, I keep forgetting about this bug.
>
>
> That's great. I can live with my hack and I await libtool 2.0. (I'll keep 
> an eye on the dev track for your patch).

I modified libtool's f77demo test case 
<http://www.pogma.com/misc/f77demo-1.0.tar.gz> and it now fails both static 
and shared :(

Seems that my original assumptions were totally wrong :( By the way if you 
look closely at libtool's c++ archive_cmds on darwin, you'll see that the 
-nostdlib bit is only used to attempt to do the same thing as 
-single_module. When the lib itself is linked -nostdlib is not there.

There are a number of things wrong here, one of them is fink's g77 package 
(maintianer CC'ed), because g77's libraries have common symbols, it is 
impossible to make shared libraries on darwin that use functions from them. 
The other problem with the static test case seems to be libtool specific, 
libtool should be adding the F77 libs when linking cprogram. I'll keep 
hacking at this, it may require that I actually brush up on my fortran, last 
used more than 15 years ago :(.

Jeffrey, I don't know if fortran will work when the libs are built 
-fno-common, I think I heard somewhere that fortran requires common symbols??

Peter

--
Peter O'Gorman - http://www.pogma.com