Fortran class pointer to attribute - compiler dependent result

Question

I'm having a problem with the following code:

module my_class
   type, public :: my_object
      real, allocatable, private :: a(:)
      real, pointer :: b => null()
   end type my_object
   interface my_object
      module procedure :: init
   end interface my_object
contains
   function init () result ( self )
      type(my_object), target :: self
      allocate( self % a(2) )
      self % a = (/ 1.0, 2.0 /)
      self % b => self % a(1)
   end function init
end module my_class


program test
   use my_class
   type(my_object) :: object
   object = my_object()
   print *, associated( object % b )
   print *, "main: ", object % b
   object % b = 7.
   print *, "main: ", object % b
end program test

Attributes a and b are initialized in the class constructor. The expected result should be:

T
main: 1.00000000
main: 7.00000000

and this I get when I use a gfortran 4.7.2 compiler, whereas code compiled with ifort 13.0.1 produces the following result:

T
main:   1.1631523E+33
main:    7.000000

which I do not understand. Where I'm making an error?

Answer 1

I tried this in ifort 14.0.1 and got the same answer as gfortran. You may have encountered a compiler bug in the old version.

Answer 2

I think that it is not a bug, the code works fine, whereas the expected results are not right. In particular, the problem with your expected "main: 1.0000" result is due to the fact the function "init", that actually initializes array "a" (thus pointer "b") to 1.0,2.0 is never called by the main program. In the main program only the constructor "my_object()" is invoked, whereas "init" is not.

At least, this is my suggestion.