StackOverflow2013

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copied!<p>The ABI of the compilers can differ. You should not pass the structures directly, but build them inside the subroutines and use pointers, which you should pass as <code>type(c_ptr)</code> or as assumed size arrays (but a copy can happen then!).</p> <p>The interoperability with C from Fortran 2003 is not meant only to interact with C but any other compiler interoperable with C. It can be a diferent Fortran compiler.</p> <p>Be aware it is against the rules of Fortran to declare the same type in more places and use it as the same type, unless the type is <code>sequence</code> or <code>bind(C)</code>. This is another reason why your program is not standard conforming.</p> <p>called.f90:</p> <pre><code>subroutine offload(cl_c) use iso_c_binding type, bind(C) :: cell_C integer :: id integer :: na, nb, nc type(c_ptr) :: a,b,c end type cell_C type cell integer :: id real, pointer :: a(:) real, pointer :: b(:) real, pointer :: c(:) end type cell type(cell) :: cl type(cell_C) :: cl_C integer :: n cl%id = cl_C%id call c_f_pointer(cl_C%a, cl%a, [cl_c%na]) call c_f_pointer(cl_C%b, cl%b, [cl_c%nb]) call c_f_pointer(cl_C%c, cl%c, [cl_c%nc]) print *, cl%a(1:10) print *, cl%b(1:10) end subroutine offload </code></pre> <p>caller.f90:</p> <pre><code>program caller use iso_c_binding type, bind(C) :: cell_C integer :: id integer :: na, nb, nc type(c_ptr) :: a,b,c end type cell_C type cell integer :: id real, allocatable :: a(:) real, allocatable :: b(:) real, allocatable :: c(:) end type cell integer :: n,i,j type(cell),target :: cl(2) type(cell_c) :: cl_c n=10 do i=1,2 allocate(cl(i)%a(n)) allocate(cl(i)%b(n)) allocate(cl(i)%c(n)) end do do j=1, 2 do i=1, n cl(j)%a(i)=10*j+i cl(j)%b(i)=10*i+j end do end do cl_c%a = c_loc(cl(1)%a) cl_c%b = c_loc(cl(1)%b) cl_c%c = c_loc(cl(1)%c) cl_c%na = size(cl(1)%a) cl_c%nb = size(cl(1)%b) cl_c%nc = size(cl(1)%c) cl_c%id = cl(1)%id call offload(cl_c) print *, cl(1)%c end program caller </code></pre> <p>with gfortran and ifort:</p> <pre><code>>gfortran called.f90 -c -o called.o >ifort caller.f90 -c -o caller.o >ifort -o a.out called.o caller.o -lgfortran >./a.out 11.0000000 12.0000000 13.0000000 14.0000000 15.0000000 16.0000000 17.0000000 18.0000000 19.0000000 20.0000000 11.0000000 21.0000000 31.0000000 41.0000000 51.0000000 61.0000000 71.0000000 81.0000000 91.0000000 101.000000 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 </code></pre> <p>No dynamic libraries necessary here.</p> <p>For 100% theoretical portability one could use <code>c_int</code>, <code>c_float</code>,... the formatting could be better and so on, but you get the point.</p> <p>You can also overload the assignments between <code>cell</code> and <code>cell_C</code> to ease the conversion.</p>

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