[Numpy-discussion] scipy.scons branch: building numpy and scipy with scons
Wed Dec 5 00:29:33 CST 2007
On Dec 5, 2007 3:11 PM, Robert Kern <email@example.com> wrote:
> I was only reading code; I haven't tested building Fortran extensions, yet.
> However, using a generic link tool would be the wrong thing to do for most
> Fortran extensions, I think. Where does it get the correct Fortran runtime
> libraries from? Some Fortran compilers really like to be the linker when mixing
Yes. SCons does not know how to do that, so I did it the "autoconf"
way: I implemented a mini library to get those linker flags, so that I
can still link C and Fortran code with gcc, not with gfortran or g77
(for example). The relevant code (+ tests) is in scons/fortran.py,
scons/fortran_scons.py + scons/tests. I have tested the parsing part
with g77, gfortran, ifort and sunfort.
> > But I may have done something wrong, because I don't know much about
> > mac os X idiosyncraties on this: basically, what's the difference
> > between -dynamiclib and -bundle ?
> > When I build python extension, I used the module scons builder, which
> > is the same than shared library except on mac os X (on mac os X,
> > shared libraries use -dynamiclib, modules use -bundle). I must confess
> > that I used the thing which worked in thise case, without knowing
> > exactly what i was doing.
> ifort only supports -dynamiclib. For the regular linker, -bundle is correct for
> building Python extensions; I may have to rethink about using ifort to link,
> then. Basically, a bundle can be dynamically loaded while dylibs can't, so
> Python uses bundles for extension modules.
Ah, that rings a bell, I remember now.
> What confuses me is that I successfully built some Fortran modules last night
> using numpy.distutils and ifort -dynamiclib. Hmm.
> >> One thing to note is that this option is only valid for GNU compilers. Linking
> >> with ifort, I need to use -Wl,-undefined,dynamic_lookup .
> > Can't we just add a linker flag instead of using it from the compiler
> > ? We still use the apple linker with ifort/icc, no ?
> I don't know. We'd have to locate all of the Fortran runtime libraries and add
> them. How do we do that? Or is that already done?
Yes, this is already done. To see how it works concretely (from the
package developer POW), you could take a look there, for example:
You use CheckF77Clib during the configuration stage, and if
successfull, this put all the relevant link flags into
env['F77_LDFLAGS']. This is more "hackish" than defining fortran
runtime and co in the tools, but also more robust. What I like with
this approach is that it is testable (you can have trivial unit tests
to test those checkers, without the need for the tested tools to be
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