gfortran 4.6 crashes with a type-bound procedure that overloads .LT.

[Janus Weil]

> I have run into erratic behavior trying to compile a module that defines
> a derived type with a component that is, in turn, another derived type
> that has a type-bound relational operator (.LT.).  Depending on the
> specifics, I sometimes get a compiler crash and sometimes successful
> completion, but wrong code.  Near-minimal code that produces a crash is
> copied below.
>
> Module DEF1 compiles OK.  But subsequently trying to compile module MESH
> produces:
>
> f951:  internal compiler error: in gfc_add_component_ref, at
> fortran/class.c:77
>
> The problem seems to be the line
>
> LST = (A%PT .LT. B%PT)
>
> in module MESH, which invokes the overloaded .LT. defined in module
> DEF1.

Note: This problem seems to be specific to type-bound operators, since
it goes away when I transform your operator ".LT." into a generic TBP
"LT" like this:

MODULE DEF1

  TYPE :: DAT
    INTEGER :: NN
    REAL :: XYZ(3)
    CONTAINS
    PROCEDURE :: LESS_THAN
    GENERIC :: LT => LESS_THAN
  END TYPE DAT

CONTAINS

  FUNCTION LESS_THAN(A, B)

    CLASS (DAT), INTENT (IN) :: A, B
    LOGICAL :: LESS_THAN

    LESS_THAN = (A%NN .LT. B%NN)

    RETURN
  END FUNCTION LESS_THAN

END MODULE DEF1

!=============================================================

MODULE MESH

  USE DEF1

  TYPE NODE
    INTEGER :: KEY
    CLASS (DAT), POINTER :: PT
    CONTAINS
    PROCEDURE :: LST
    GENERIC :: LT => LST
  END TYPE NODE

CONTAINS

  FUNCTION LST (A, B)

    CLASS (NODE), INTENT (IN) :: A, B
    LOGICAL :: LST

    IF (A%KEY .GT. 0 .AND. B%KEY .GT. 0) THEN
      LST = (A%KEY .LT. B%KEY)
    ELSE
      LST = A%PT%LT(B%PT)
    END IF

    RETURN
  END FUNCTION LST

END MODULE MESH


Cheers,
Janus