Re: [RFC, PATCH, fortran] PR fortran/60255 Deferred character length

[Dominique d'HumiÃres <dominiq at lps dot ens dot fr>]

Dear Andre,

The patch causes an ICE for the test gfortran.dg/unlimited_polymorphic_1.f03:

f951: internal compiler error: in gfc_add_component_ref, at fortran/class.c:236

f951: internal compiler error: Abort trap: 6
gfc: internal compiler error: Abort trap: 6 (program f951)
Abort

Reduced test for which the ICE is triggered by âlen(w)'

MODULE m

contains
  subroutine bar (arg, res)
    class(*) :: arg
    character(100) :: res
    select type (w => arg)
      type is (character(*))
        write (res, '(I2)') len(w)
    end select
  end subroutine

END MODULE

Note that with your patch at https://gcc.gnu.org/ml/fortran/2014-08/msg00022.html, I get the same ICE for the Mikaelâs test at https://gcc.gnu.org/ml/fortran/2014-08/msg00055.html (before your patch for pr60255, it used to give a wrong length: 80 instead of 20 AFAICR).

Note that the assert at fortran/class.c:236 is also triggered for pr61115.

Thanks for working on these issues,

Dominique

>> On 8 December 2014 at 18:38, Andre Vehreschild <vehre@gmx.de> wrote:
>> Hi all,
>> 
>> please find attached a more elaborate patch for pr60255. I totally agree that
>> my first attempt was just scratching the surface of the work needed.
>> 
>> This patch also is *not* complete, but because I am really new to gfortran
>> patching, I don't want to present a final patch only to learn then, that I have
>> violated design rules, common practice or the like. Therefore please comment
>> and direct me to any sources/ideas to improve the patch.
>> 
>> Topic:
>> The pr 60255 is about assigning a char array to an unlimited polymorphic
>> entity. In the comments the concern about the lost length information is
>> raised. The patch adds a _len component to the unlimited polymorphic entity
>> (after _data and _vtab) and adds an assignment of the string length to _len
>> when a string is pointer assigned to the unlimited poly entity. Furthermore is
>> the intrinsic len(unlimited poly pointing to a string) resolved to give the
>> _len component.
>> 
>> Yet missing:
>> - assign _len component back to deferred char array length component
>> - transport length along chains of unlimited poly entities, i.e., a => b; c =>
>>  a where all objects are unlimited poly and b is a string.
>> - allocate() in this context
>> 
>> Patch dependencies:
>> none
>> 
>> Comments, concerns, candy welcome!
>> 
>> Regards,
>>        Andre