[GRASS5] Re: [DebianGIS] grass and 64bit

[Glynn Clements]

Hamish wrote:

> > To successfully compile GRASS on 64bit platforms, the required
> > FFTW2 library has to be compiled with -fPIC flag:
> > 
> >     #applies to FFTW2, not GRASS:
> >     cd fftw-2.1.5/
> >     CFLAGS="-fPIC" ./configure
> >     make
> >     make install

This is true on any platform if FFTW is a static library and the GRASS
libraries (specifically libgrass_gmath) are dynamic libraries. In
practice, the safest option is to always use -fPIC for both static and
shared libraries. Static libraries compiled without -fPIC can only be
used directly by executables, and not by shared libraries.

> Now we (theoretically) can compile GRASS with TclTk 8.4, maybe someone 
> who knows how can help to bring FFTW into the modern era as well, i.e. 
> to use fftw3 not fftw2.
> 
> #ifdef 's to remain backwards compat with v.2 ?

If we don't care about supporting FFTW 2.x, the changes to
lib/gmath/fft.c to use 3.x instead are trivial.

Supporting both 2.x and 3.x would be quite a bit more work due to the
necessary configure.in changes.

-- 
Glynn Clements <glynn at gclements.plus.com>