[Bug fortran/67883] ICE on empty array constructor of character function

["gerhard dot steinmetz dot fortran at t-online dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67883

--- Comment #2 from Gerhard Steinmetz <gerhard.steinmetz.fortran@t-online.de> ---

Another group of examples.
First case is working in a sufficient manner.
Concatenating two empty hulls (zero len and size, respectivly)
gives an empty hull as result again.


$ cat zz1.f90
program p
   character(*), parameter :: c1(*) = [character(*) :: 'a'] // [character(*) ::
'z']
   character(*), parameter :: c2(*) = [character(0) ::] // [character(0) ::]
   character(*), parameter :: c3(*) = [character(0) ::] // [character(*) ::]
   character(*), parameter :: c4(*) = [character(0) ::]
   print *, 'c1: ', len(c1), size(c1), c1
   print *, 'c2: ', len(c2), size(c2), c2
   print *, 'c3: ', len(c3), size(c3), c3
   print *, 'c4: ', len(c4), size(c4), c4
end


$ gfortran-6 -g -O0 -Wall -fcheck=all zz1.f90
$ a.out
 c1:            2           1 az
 c2:            0           0
 c3:            0           0
 c4:            0           0

---


Next case is questionable : no error, unexpected results.


$ cat zz2.f90
program p
   character(*), parameter :: c5(*) = [character(*) :: 'a'] // [character(0)
::]
   character(*), parameter :: c6(*) = [character(0) ::] // [character(*) ::
'z']
   print *, 'c5: ', len(c5), size(c5), c5
   print *, 'c6: ', len(c6), size(c6), c6
end


$ gfortran-6 -g -O0 -Wall -fcheck=all zz2.f90
$ a.out
 c5:            0           0
 c6:            0           0



Errors detected with alternative code :

$ cat zz3.f90
program p
   character(*), parameter :: b1(*) = [character(*) :: 'a']
   character(*), parameter :: b2(*) = [character(0) ::]
   character(*), parameter :: b3(*) = b1 // b2
!  character(*), parameter :: b4(*) = b2 // b1
   print *, 'b1: ', len(b1), size(b1), b2
   print *, 'b2: ', len(b2), size(b2), b2
   print *, 'b3: ', len(b3), size(b3), b3
!  print *, 'b4: ', len(b4), size(b4), b4
end


$ gfortran-6 -g -O0 -Wall -fcheck=all zz3.f90
zz3.f90:4:37-43:

    character(*), parameter :: b3(*) = b1 // b2
                                     1     2
Error: Shapes for operands at (1) and (2) are not conformable
zz3.f90:8:24:

    print *, 'b3: ', len(b3), size(b3), b3
                        1
Error: 'string' argument of 'len' intrinsic at (1) must be CHARACTER
zz3.f90:8:34:

    print *, 'b3: ', len(b3), size(b3), b3
                                  1
Error: 'array' argument of 'size' intrinsic at (1) must be an array