How to make a Fortran c_ptr null?

Question

I have a type with two pointers, one Fortran pointer and one C pointer:

type mytype
  procedure(whatever), pointer, nopass :: fortranPointer
  type(c_ptr) :: cPointer
end type

I can assign something to both pointers like:

type(mytype) :: instance
instance%fortranPointer => fPtrToSomething
instance%cPointer = c_loc(somethingElse)

When I want to initialize the pointers without assigning something, I can use null() or nullify for the Fortran pointer:

instance%fortranPointer => null()

But how can I initialize the c_ptr to null? instance%cPointer = null() is not working as null() is not allowed on the right hand side of an assignement. c_loc(null()) is not allowed as null() is not a variable, which location can be obtained.

Is there something like a c_null?

PVitt · Accepted Answer · 2017-01-16 13:51:08Z

3

Figured out that there is a ~~intrinsic type~~ named constant c_null_ptr that can be used.

edited Jan 16, 2017 at 13:51

answered Jan 26, 2015 at 10:56

PVitt

11.8k5 gold badges54 silver badges85 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

francescalus Over a year ago

As a minor correction, c_null_ptr isn't an intrinsic type itself, but is a named constant of type c_ptr (so suitable for assignment and initialization for other variables of that type).

PVitt Over a year ago

@francescalus Thanks. Wasn't aware of this internals.

zbeekman Over a year ago

Does one use pointer assignment or normal assignment to set a c_ptr to c_null_ptr?

Collectives™ on Stack Overflow

How to make a Fortran c_ptr null?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related