Varying length character strings by John Reid

[John Chludzinski]

Just looking for a version of ISO_VARYING_STRING that's supported as
part of the standard.

On Tue, Jan 29, 2013 at 3:36 AM, Tobias Burnus <burnus@net-b.de> wrote:
> John Chludzinski wrote:
>>
>> Should the code contained in:
>> ftp://ftp.nag.co.uk/sc22wg5/N1901-N1950/N1913.txt be compilable using
>> the gfortran compiler?
>
>
> Eventually yes, but deferred-length/allocatable-length strings as components
> of derived types aren't yet supported; thus, the following fails:
>
> type VARYING_STRING
>   CHARACTER(LEN=:),ALLOCATABLE :: chars
> end type VARYING_STRING
>
> That's tracked at http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51976
>
> Implementing it is not that simple as it requires some changes how to
> compiler internally handles string lengths.
>
> (Note to gfortran developers: One issue is that the gfc_charlen (e.g.
> "ts.u.cl") is shared (cf. ts.u.cl->length->...->backend_decl). Additionally,
> the length will have to be something like "dt%comp%hidden_length_comp", i.e.
> "dt%comp%" has to be added at all places. A half-working version, which
> updates se.string_length is not that difficult, but some hard issues remain.
> Note 2: When implementing it, keep DT length-type parameter in mind, when
> used as "character(len=lenght_param) :: comp", the issues are nearly
> identical.)
>
>
>> PURE FUNCTION s_to_c(string) ! generic CHAR
>>   1
>> Error: CHARACTER(*) function 's_to_c' at (1) cannot be pure
>
>
> I think here the compiler confused character(len=*) with character(len=:);
> that has been fixed in GCC 4.8, but one runs into an internal compiler
> error:
>
> foo.f90: In function 's_to_c':
> foo.f90:5:0: internal compiler error: in gfc_add_modify_loc, at
> fortran/trans.c:159
>      s_to_c = string
>  ^
> 0x5b8e97 gfc_add_modify_loc(unsigned int, stmtblock_t*, tree_node*,
> tree_node*)
>         ../../gcc/fortran/trans.c:158
> 0x5f3af0 alloc_scalar_allocatable_for_assignment
>         ../../gcc/fortran/trans-expr.c:7629
>
>
> The latter issue is now tracked at
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56138
>
> Tobias