[Bug fortran/49638] [OOP] length parameter is ignored when overriding type bound character functions with constant length.

["mikael at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49638

--- Comment #12 from Mikael Morin <mikael at gcc dot gnu.org> 2011-08-04 11:14:36 UTC ---

If we are willing to do some simple expression comparisons, here is what I
think should be supported (most common cases):

 - constants: this is the minimum
 - variables/dummies: for the case len=n
 - sub-components: for the case len=derived%char_length_comp
 - function calls: for the case len=len(some_char)
 - arithmetic operators: for the case len=n+1

So, only missing in your preliminary patch are sub-components and function.



(In reply to comment #9)
> > I don't know however how you will have two corresponding dummy
> > arguments (from different procedures) compare equal.
> 
> Well, the patch in comment #7 handles this by just comparing the names of the
> arguments (which have to be the same in overridden procedures, so I this this
> will be enough):
> 
> +    case EXPR_VARIABLE:
> +      if (strcmp (e1->symtree->n.sym->name, e1->symtree->n.sym->name) != 0)
> +    return FAILURE;
> 
Ah, yes. 

> 
> gfc_dep_compare_expr relies on a function called 'gfc_are_identical_variables'.
> This really checks for equal symbols, which is too strict for our case here (so
> we may add an extra argument to loosen this restriction?).
Yes, makes sense. Then you have components and functions almost for free.