问题
I have a structured type in Fortran that contains lots of data including pointers (real*8 pointer data type).
I am developing a C++ API for some Fortran routine. I need the contents of the structure to persist between calls to the Fortran routine.
I was thinking about getting the address of the structure using loc and pass the address to the C++ side.
When Fortran routine is called again from C++ and the address is passed back to Fortran, somehow typecast it to the original structure and then use it for computation.
What approach can I use to accomplish this?
Thanks.
EDIT: my code based on the comments/suggestions. The program crashes when C_LOC is called (if I comment out the call to C_LOC then the program does not crash).
subroutine TEST(a,b,c,d,e,mystruct,ier) BIND(C, NAME='TEST')
use mymodule
USE, INTRINSIC :: ISO_C_BINDING
implicit none
TYPE(C_PTR) :: mystruct
TYPE(mymodule), TARGET :: origstruct
INTEGER :: a, b, c
DOUBLE PRECISION :: d(*), e(*)
INTEGER :: ier
!Do something with origstruct and other arguments
print *, 'here 1'
mystruct= C_LOC(origstruct)
print *, 'here 2'
end
回答1:
Under Fortran 2003 (supported by most compilers nowadays), you can use the standard ISO_C_BINDING module. If you are happy with the obtained C pointer being "opaque" (that is, you just want a void*
), you can use the C_LOC
function:
use, intrinsic :: ISO_C_BINDING
type(your_struct_t), target :: your_obj
type(C_PTR) :: p
p = C_LOC(your_obj)
You can then pass this pointer to some C procedure:
interface
subroutine mycproc(x, n, userdata) bind(C)
use, intrinsic :: iso_c_binding
integer(c_int), intent(in), value :: n
real(c_double), intent(in) :: x(n)
type(c_ptr), intent(in), value :: userdata
end subroutine
end interface
call mycproc(x, size(x), p)
来源:https://stackoverflow.com/questions/42681622/passing-a-structured-data-type-from-fortran-to-c