Is it possible to call a Fortran subroutine from C/C++, where one of the Fortran arguments is a deferred-shape array? (Hopefully I'm using the term "deferred-shape" correctly.)
In the example below, subr1() uses explicit-shape, and works fine, but subr2() uses deferred-shape and causes a segfault. This question indicates that one needs an explicit interface to call subr2() from another Fortran subroutine, but I'm trying to call from C. Is it just not possible to do it this way?
In the real problem the length of the array would be more complicated -- which is why, in an ideal world, I would like to use the deferred-shape version. (Of course in an ideal world, I wouldn't be mixing Fortran and C at all.)
test_array_c.c
#include <malloc.h>
extern void subr1_(int*, int*);
extern void subr2_(int*, int*);
int main(int argc, char **argv){
int N,i;
int *data;
// create an array
N=3;
data=(int*)malloc(N*sizeof(int));
for (i=0;i<N;i++) data[i]=i;
// pass array to fortran functions
subr1_(&N,data);
subr2_(&N,data);
// free
free(data);
}
test_array_f90.f90
subroutine subr1(n,data)
implicit none
integer,intent(in) :: n
integer,intent(in) :: data(n)
integer :: i
do i=1,n
print*, data(i)
enddo
end subroutine
subroutine subr2(n,data)
implicit none
integer,intent(in) :: n
integer,intent(in) :: data(:)
integer :: i
do i=1,n
print*, data(i)
enddo
end subroutine
command line build/run
user@host:~$ gcc -g -O0 -c test_array_c.c
user@host:~$ gfortran -g -O0 -c test_array_f90.f90
user@host:~$ gcc -o test_array test_array_c.o test_array_f90.o -lgfortran
user@host:~$ ./test_array
0
1
2
Segmentation fault (core dumped)
