mixed language linking error

[jz001]

Hello,

I'm trying ot integrate a Unix domain socket C routine into my Fortran90 program. Therefore I've created a simple test example. I'm using openSUSE 11.1, Intel Fortran Compiler 11.1 and Intel C Compiler 11.1.

The C routine:

// C++ - Routine
#include
#include
extern "C" void pythagoras (float a, float b, float *c)
{
*c = (float) sqrt(a*a+b*b);
}

The Fortran program:

module cproc
interface
subroutine pythagoras (a, b, res )
! DEC$ ATTRIBUTES C :: pythagoras
! DEC$ ATTRIBUTES REFERENCE :: res
real :: a, b, res
end subroutine
end interface
end module


program fmain
use cproc
implicit none
real :: x, y, z

write (* ,*) ' Berechnung der Hypotenusenlaenge eines rechtwickligen Dreiecks '
write (* ,*) ' Geben Sie die beiden Seitenlaengen ein , die den rechten Winkel '
write (* ,*) ' einschliessen :'
read (* ,*) x, y

call pythagoras (x,y,z)
write (* ,*) ' Die Laenge der Hypotenuse betraegt : ', z
end program fmain


The C routine is compiled by:

icc -c crout.cpp

The program then is compiled and linked by:

ifort fmain.f90 crout.o -cxxlib -o prog.out

The error message:

/tmp/ifortMMrDlc.o: In function `MAIN__':
fmain.f90:(.text+0x170): undefined reference to `pythagoras_'

occurs.

Is there is someone who can help me?

Thanks in advance.
jz001

[Tim_Gallagher · Accepted solution]

Put the .o file before the .f90 file on the ifort command line, and if that doesn't do it, try adding the underscore _ to the end of the C routine name and recompiling.

Tim

[mecej4]

The Mixed Language Programming chapter of the Intel Fortran Users Guide will help you with this program. You should read about the different possible ways of linking C/C++ with Fortran, and make a selection suited to your needs.

The default calling convention for Fortran is by address, and the default symbol decoration is to append an underscore. One solution is to change the C++ routine to

// C++ - Routine
#include
extern "C" void pythagoras (float *pA, float *pB, float *c)
{float a=*pA, b=*pB;
*c = (float) sqrt(a*a+b*b);
}

and to compile using:

g++ -c pyth.cpp
ifort -assume nounderscoring fmain.f90 pyth.o

[TimP]

Needless to say, if portable code is acceptable, you should be using the ISO C interoperability implemented in all Fortran compilers of the last few years.

[jz001]

@Tim

Tanks it works