c++ program calling a Fortran subroutine with a function in the arg.

[taku]

Hello!.

This is my second post, and my first post was successful.
I have a new problem; i want to call a subroutine's fortran which have a function in the argument and the compilation ran properly, but when i execute the program this shows me an "Segmentation fault".

This is my c++ program:

//Main.cpp
#include <stdio.h>
#include <iostream>
#include <cmath>
#include <complex>

using namespace std;

struct Naa{
	double x;
	void operator()(double xaux){
		x = xaux*xaux;
	}
};


extern"C" {
	void usefunc_(double *a, double *b, Naa *Func, double *CRES);
}

int main(){
	double a = 0.0;
	Naa AA;
	double b = 1.0;
	double Func = 1;
	double CRES;
	usefunc_(&a, &b, &AA, &CRES);
	cout<<"The result is: "<< CRES <<endl;
	
	return 0;
}

And my fortran's code is:

!FunOFun.f90 
SUBROUTINE usefunc(XL,XU,BF, BRES)
	IMPLICIT REAL *8 (A-B,D-H,O-Z)
	BRES = (XU-XF)/((BF(XU))*2)
	PRINT *,BRES
	END subroutine usefunc

I compiled with GNU compiler like this:

g++ -O0 -g -c Main.cpp
gfortran -O0 -g -c FunOFun.f90 -frecord-marker=8
g++ -O0 -g -o a.test FunOFun.o Main.o -frecord-marker=8 -lgfortran

I appreciate if someone could give me a hand.

Thanks a lot.

Taku.

[Rubberman]

Remember, Fortran calling conventions pass arguments in reverse C/C++. So, in your "extern C" declaration, switch the function arguments back-to-front. It's been a donkey age since I had to integrate Fortran/F77 with C languages, but this is what I remember as the major caveat.

[taku]

Thanks for the tip. I tried it but this dont solve the problem.