Basic example of how to call c++ code from fortran

compile.bat

gcc -c test.cpp -o test.o
gfortran main.f90 test.o
a

main.f90

program toto
	integer::a,b,c
	!external ADD
	a=10
	b=15
	call ADD(a,b,c)
	
	print*, a,b,c
end program

test.cpp

extern "C"
{
	extern void add_(int* a, int* b, int* c);
}
void add_(int* a, int* b, int* c)
{
	*c=*a+*b+0;
	return;
}