[patch,gfortran] PR 22607: PURE return-by-reference functions

[Erik Edelmann]

:ADDPATCH fortran:

Here's a patch for PR 22607; PURE (including ELEMENTAL)
return-by-reference functions don't currently work.  If we
avoid setting

        DECL_IS_PURE (fndecl) = 1;

in trans-decl.c(build_function_decl), the problem is fixed.

I do, however, not know much about the backend.  Among the things
I don't know is whether DECL_IS_PURE (fndecl) = 1 is supposed to
work for return-by-ref. functions or not (might this actually be
a backend bug?).  Comments from people with better understanding
of the backend are wellcome.

Bootstrapped & tested on Linux/x86, Ok?


        Erik


2005-11-08  Erik Edelmann  <eedelman@gcc.gnu.org>

        PR fortran/22607
        * trans-decl.c(build_function_decl): Don't set 
        DECL_IS_PURE (fndecl) = 1 for return-by-reference
        functions.


2005-11-08  Erik Edelmann  <eedelman@gcc.gnu.org>

        PR fortran/22607
        * gfortran-dg/pure_byref_1.f90: New.
        * gfortran-dg/pure_byref_2.f90: New.
-------------- next part --------------
Index: gcc/fortran/trans-decl.c
===================================================================
--- gcc/fortran/trans-decl.c	(revision 106653)
+++ gcc/fortran/trans-decl.c	(working copy)
@@ -1203,7 +1203,7 @@
       /* TODO: check if a pure SUBROUTINE has no INTENT(OUT) arguments
 	 including a alternate return. In that case it can also be
 	 marked as PURE. See also in gfc_get_extern_function_decl().  */
-      if (attr.function)
+      if (attr.function && !gfc_return_by_reference (sym))
 	DECL_IS_PURE (fndecl) = 1;
       TREE_SIDE_EFFECTS (fndecl) = 0;
     }
-------------- next part --------------
! { dg-do compile }
! PR 22607: PURE/ELEMENTAL return-by-reference functions
program main
  implicit none
  character(2), dimension(2) :: a, b
  a = 'ok'
  b = fun(a)
  if (.not.all(b == 'ok')) call abort()
contains
  elemental function fun(a) 
    character(*), intent(in) :: a
    character(len(a)) :: fun
    fun = a
  end function fun
end program main
-------------- next part --------------
! { dg-do compile }
! PR 22607: PURE return-by-reference functions
program main
  implicit none
  integer, dimension(2) :: b
  b = fun(size(b))
  if (b(1) /= 1 .or. b(2) /= 2) call abort()
contains
  pure function fun(n) 
    integer, intent(in) :: n
    integer :: fun(n)
    integer :: i
    do i = 1, n
        fun(i) = i
    end do
  end function fun
end program main