Thread: External Functions and Compiler linking issues

Hey,

Ok here goes...
I needed to separate a function (mmult) I had made from the driver program so I put it in its own .c file. The C driver though calls mmult.c and other Fortran functions so i needed to compile it using the fortran compiler. The mmult function uses OpenMp directives and so I need to use the intel compiler with the -openmp switch to take advantage, as g77 doesn't seem to support openMP.

Ok...

I can compile ok with without openMp support
>f77 -o mm mm.c mmult.c dgemm.o xerbla.o lsame.o
but when I try to use the fortran compiler (with or without omp)...
>ifort -openmp -o mm mm.c mmult.c dgemm.o xerbla.o lsame.o
I get ...

mm.c: file not recognized: File format not recognized

I think it's because it wants the object file.

This is where my problem comes in...
- I can't compile the mm.c file on it's own because it needs the fortran functions.
- I can't compile the mmult.c as it hasn't got a main i think:

/usr/lib/crt1.o(.text+0x18): In function `_start':
../sysdeps/i386/elf/start.S:115: undefined reference to `main'

Any ideas what i'm supposed to do here?

Thanks,

Colly

Oh - has anyone got any idea where I can get help with modifying my matrix multiplier (based on DGEMM) to work with OpenMP?

Thanks.

I am EXTREMELY interested in hearing how you do combine the languages, as I know C/C++ much better than fortran, but I do need fortran at times to do some maths...

Like I said they can be linked fine. It's just with the intel compiler that I can't get it to compile. f77 and g77 work fine
>f77 -o mm mm.c mmult.c dgemm.o xerbla.o lsame.o
compiles just file.

how about compiling the fortran functions first?

Yeah I had actually compiled them all separately, but can you tell me how do the linking of all the files using the C compiler instead of the Fortran compiler - I was doing it the fortran way because apparently "...the fortran compiler knows where the C libraries are but the C compiler has to be told where the fortran libraries are...". And to be honest with you my compiler doesn't listen to me much anyway.

If its possible to compile a C file without a main then there must be something wrong with my code... or do i need to use a compiler arg?

Code:

//mmult.c
#include <stdlib.h>
#include <stdio.h>
#ifdef _OPENMP
#include <omp.h>
#endif /* OPENMP */

typedef enum
{
  FALSE,
  TRUE
} boolean;

int mmult_(char *transA, char *transB, int *m_rows, int *n_cols, int *k_common, double *alpha, double *matrixA, int *lda, double *matrixB, int *ldb, double *beta, double *matrixC, int *ldc);

int mmult_(char *transA, char *transB, int *m_rows, int *n_cols, int *k_common, double *alpha, double *matrixA, int *lda, double *matrixB, int *ldb, double *beta, double *matrixC, int *ldc)
{...
}

Code:

//mm.c (driver)
...
extern int mmult_(char *transA, char *transB, int *m_rows, int *n_cols, int *k_common, double *alpha, double *matrixA, int *lda, double *matrixB, int *ldb, double *beta, double *matrixC, int *ldc);
...

That's ok isn't it??

Thanks,

Colly