Some problems with deferred character length

[MR]

Hi all,

while experimenting with ifort support for deferred length character (please, consider that my understanding of this feature is far from being good!) I see some errors for the following code depending on the compilation flags.

module m
 implicit none
contains
 subroutine s(x,dims)
  class(*), allocatable, intent(out) :: x(:)
  integer,  allocatable, intent(out) :: dims(:)

   allocate(dims(2))
   dims(1) = 2
   dims(2) = 4

   allocate(character(len=dims(2))::x(dims(1))) ! no problems using len=4
   select type(x); type is(character(len=*))
    x = 'ABCD'
   end select

 end subroutine s
end module m


program test
 
 use m
 implicit none
 integer, allocatable :: d(:)
 class(*), allocatable :: t(:)

  call s(t,d)
  select type(t); type is(character(len=*))
   write(*,*) t
  end select
end program test

The results are:

1) no compiler flags: works as expected
$ ifort test.f90 -o test
$ ./test
 ABCDABCD

2) with -check all: there is an error
$ ifort -check all -traceback test.f90 -o test
$ ./test
forrtl: severe (408): fort: (8): Attempt to fetch from allocatable variable DIMS when it is not allocated

Image              PC                Routine            Line        Source             
test               0000000000405550  Unknown               Unknown  Unknown
test               0000000000402337  m_mp_s_                     4  test.f90
test               000000000040354C  MAIN__                     28  test.f90
test               00000000004021FE  Unknown               Unknown  Unknown
libc.so.6          00007F04B80A3DB5  Unknown               Unknown  Unknown
test               0000000000402109  Unknown               Unknown  Unknown

3) the error is slightly different including -standard-semantics
$ ifort -check all -traceback -standard-semantics test.f90 -o test
$ ./test
forrtl: severe (408): fort: (2): Subscript #1 of the array DIMS has value 2 which is greater than the upper bound of -1

Image              PC                Routine            Line        Source             
test               0000000000405470  Unknown               Unknown  Unknown
test               000000000040242D  m_MP_s_                     4  test.f90
test               0000000000403465  MAIN__                     28  test.f90
test               00000000004021FE  Unknown               Unknown  Unknown
libc.so.6          00007F81EC70FDB5  Unknown               Unknown  Unknown
test               0000000000402109  Unknown               Unknown  Unknown

$ ifort -V
Intel(R) Fortran Intel(R) 64 Compiler XE for applications running on Intel(R) 64, Version 15.0 Build 20140723

Marco

[Steven_L_Intel1]

There are several problems here I need to work through... I'll let you know what I find.

[mecej4]

Perhaps it is significant/telling that the error is reported on line-4, the subroutine statement, rather than later. When execution reaches this line, the output array dims has neither been allocated nor initialized, and the compiler seems to be unable to set up the stack.

[Steven_L_Intel1]

The INTENT(OUT) is probably involved to some extent - the compiler is incorrectly doing bounds and pointer checking on the unallocated dummy argument - I have a faint memory of a similar issue being reported before. Stay tuned.

[Steven_L_Intel1]

Well, it's not the INTENT(OUT). What is particularly interesting about this program is that if you compile it with no options, that is, with optimization, it works, but when I tried it with optimization disabled, I got a segfault! Either one of the arguments seems to trigger the problem.

I have escalated this to development as issue DPD200363248. Thanks.

[MR]

Steve, thank you. (By the way, it helps so much that you report the tracking code and later on when things get fixed!)

Marco

[Steven_L_Intel1]

This has been fixed in our sources. I expect the fix to appear in Update 2, planned for February.