[Bug fortran/67177] New: MOVE_ALLOC not automatically allocating deferred character arrays in derived types

[templed at tcd dot ie]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67177

            Bug ID: 67177
           Summary: MOVE_ALLOC not automatically allocating deferred
                    character arrays in derived types
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: templed at tcd dot ie
  Target Milestone: ---

(First time submitting a bug, apologies if I've messed up somewhere)

When a derived type containing a deferred-length character variable is the TO=
argument of a MOVE_ALLOC() call the character length is not correctly set and
the value of the variable is not stored.

Two workarounds for this is to either not use deferred-length character
variables (use an allocatable array of single characters), or to preallocate
the length to the variable that will be the TO= argument.

The below test program has been tested with Intel 15.0.2 (20150121) and, when
the line critical line is commented out (see code) the program correctly
allocates the deferred-length string and populates it with the correct value.
In gfortran 5.2 (and 4.9.2, FWIW) it fails to allocate the length and store the
value even though a check with allocated() returns true.


$ gfortran -v
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/usr/support/modules/gnu-5.2/libexec/gcc/x86_64-unknown-linux-gnu/5.2.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../configure --prefix=/usr/support/modules/gnu-5.2
--disable-multilib
Thread model: posix
gcc version 5.2.0 (GCC) 


Test program:

program str
implicit none

type string
  character(:), Allocatable :: text
end type string

type strings
  type(string), allocatable, dimension(:) :: strlist
end type strings

type(strings) :: teststrs
type(string) :: tmpstr
integer :: strlen = 20

allocate(teststrs%strlist(1))
allocate(character(len=strlen) :: tmpstr%text)

! This is the critical line. If this is commented then
! the move_alloc fails. Whereas what should happen is that
! this variable should be allocated automatically by move_alloc
allocate(character(len=strlen) :: teststrs%strlist(1)%text)


! Needs blanking otherwise memory is leaked
tmpstr%text(1:20) = ' '
tmpstr%text(1:3) = 'foo'
! Should return "alloc?, strlen F        20" when the critical line is
commented out (shows 'T' otherwise)
write(*,*)'alloc?, strlen
',allocated(teststrs%strlist(1)%text),len(tmpstr%text)
call move_alloc(tmpstr%text,teststrs%strlist(1)%text)
! Should return "alloc?, strlen T        20"
write(*,*)'alloc?, strlen
',allocated(teststrs%strlist(1)%text),len(teststrs%strlist(1)%text)
! Should return "foo                 "
write(*,*)'"',teststrs%strlist(1)%text,'"'

end program str