How to pass an array to Fortran 95 from C??

[vibe33]

I'm trying to call routines in the SHTOOLS library (written in fortran 95) from C. For example, one routine is:

subroutine PreCompute(lmax, zero, w, plx, wisdom_file, norm, csphase, cnorm)

integer, intent(in) :: lmax
real*8, intent(out) :: zero), w)
real*8, intent(out), optional :: plx,
integer, intent(in), optional :: norm, csphase, cnorm
character(*), intent(in), optional :: wisdom_file

if (size(zero) < lmax+1) then
print*, "Error --- PreCompute"
...

Now when I call from C, I use the standard:

int lmax;
double *zero = malloc(...);
precompute_(&lmax, zero, ...)

but apparantly fortran 95 needs to know the size of the 'zero' array since it checks size(zero) etc. Needless to say, this check fails since it doesn't have size information on 'zero'.

My question is, how do you properly pass arrays to fortran 95? How do you specify these size/dimension parameters in the call?

 

[xwb]

Which compiler are you using?

If your Fortran 95 compiler supports the 2003 standard then there already is a C interface.

If it does not support the 2003 standard, then there will be some vendor specific technique but we need to know which compiler you're using first.

 

[vibe33]

Oh yes I'm using gfortran:

GNU Fortran (GCC) 4.1.2 20080704 (Red Hat 4.1.2-48)

 

[xwb]

Examples in

http://www.fortran.bcs.org/2002/interop.htm

http://coding.derkeiler.com/Archive/C_CPP/comp.lang.c/2009-02/msg03505.html

Just search for ISO_C_BINDING on the net.