calling c. subroutine from fortran

sailschooner · 02-25-2018, 05:52 AM

I'm trying to use the following no problem gcc-compilable proram

void sub_(i,j,k)
int *i, *j, *k;
{
*k = *i + *j;
return;
}

as a subroutine in a Lahey lf95 fortran program:

PROGRAM MAIN
integer :: i,j,k
i = 12
j = 43
k = 0
print *, 'Before: i,j,k=',i,j,k
call sub(i,j,k)
print *, 'After: i,j,k=',i,j,k
stop
end

Obviously the fortran part needs compiling, but do I use sub.c or sub.o (or something else). What would be the command to run them? Also, am I likely to need USE and/or INCLUDE, I intend to build them into a line-plotting program later. Many thanks

Adrian

norobro · 02-25-2018, 10:24 AM

I don't know anything about Lahey fortran but here's how to compile with gfortran:

Code:

$ gfortran -c fort_file.f95
$ gcc -c c_file.c
$ gfortran -o app fort_file.o c_file.o
$ ./app
 Before: i,j,k=          12          43           0
 After: i,j,k=          12          43          55

HTH

masterclassic · 02-26-2018, 12:02 PM

Hello.
I didn't use Lahey fortran since early 90s, however I remember well that an issue in multiple language programming is related to how the procedures/subroutines communicate their arguments: by reference or by value. You have to use the same on both parts.

astrogeek · 02-26-2018, 02:22 PM

Please place your code snippets inside [CODE]...[/CODE] tags for better readability. You may type those yourself or click the "#" button in the edit controls.

Quote:

Originally Posted by sailschooner

Obviously the fortran part needs compiling, but do I use sub.c or sub.o (or something else). What would be the command to run them?

norobro has provided the answer - build the object files separately from fortran and C source files, then build the application from the object files.

sundialsvcs · 02-27-2018, 07:58 AM

Quote:

Originally Posted by masterclassic

Hello.
I didn't use Lahey fortran since early 90s, however I remember well that an issue in multiple language programming is related to how the procedures/subroutines communicate their arguments: by reference or by value. You have to use the same on both parts.

A traditional problem with FORTRAN is both "pass by value or reference" and the in-memory layout of arrays. Some FORTRANs use a "column-major format" where most languages use "row-major."

Naturally, you must also get the "calling sequence" right – exactly how parameters are passed to-and-from the subroutine. But that's true of any language implementation.

The documentation of any compiler should contain a substantial section discussing exactly how to call to or from its subroutines, how to build and use binary libraries of various kinds (dynamic or static), and so on. Probably giving examples.