Re: [Patch 1/2, Fortran, pr60322] [OOP] Incorrect bounds on polymorphic dummy array

[Mikael Morin <mikael dot morin at sfr dot fr>]

Le 23/03/2015 13:43, Andre Vehreschild a écrit :
> Hi Mikael,
> 
> thanks for looking at the patch. Please note, that Paul has sent an addendum to
> the patches for 60322, which I deliberately have attached.
> 
>>  26/02/2015 18:17, Andre Vehreschild a écrit :
>>> This first patch is only preparatory and does not change any of the
>>> semantics of gfortran at all.
>> Sure?
> 
> With the counterexample you found below, this of course is a wrong statement.
>  
>>> diff --git a/gcc/fortran/expr.c b/gcc/fortran/expr.c
>>> index ab6f7a5..d28cf77 100644
>>> --- a/gcc/fortran/expr.c
>>> +++ b/gcc/fortran/expr.c
>>> @@ -4059,10 +4060,10 @@ gfc_lval_expr_from_sym (gfc_symbol *sym)
>>>    lval->symtree = gfc_find_symtree (sym->ns->sym_root, sym->name);
>>>  
>>>    /* It will always be a full array.  */
>>> -  lval->rank = sym->as ? sym->as->rank : 0;
>>> +  as = sym->as;
>>> +  lval->rank = as ? as->rank : 0;
>>>    if (lval->rank)
>>> -    gfc_add_full_array_ref (lval, sym->ts.type == BT_CLASS ?
>>> -			    CLASS_DATA (sym)->as : sym->as);
>>> +    gfc_add_full_array_ref (lval, as);
>>
>> This is a change of semantics.  Or do you know that sym->ts.type !=
>> BT_CLASS?
> 
> You are completely right. I have made a mistake here. I have to tell the truth,
> I never ran a regtest with only part 1 of the patches applied. The second part
> of the patch will correct this, by setting the variable as depending on whether
> type == BT_CLASS or not. Sorry for the mistake.
> 
>>> diff --git a/gcc/fortran/trans-decl.c b/gcc/fortran/trans-decl.c
>>> index 3664824..e571a17 100644
>>> --- a/gcc/fortran/trans-decl.c
>>> +++ b/gcc/fortran/trans-decl.c
>>> @@ -1013,16 +1017,24 @@ gfc_build_dummy_array_decl (gfc_symbol * sym, tree
>>> dummy) tree decl;
>>>    tree type;
>>>    gfc_array_spec *as;
>>> +  symbol_attribute *array_attr;
>>>    char *name;
>>>    gfc_packed packed;
>>>    int n;
>>>    bool known_size;
>>>  
>>> -  if (sym->attr.pointer || sym->attr.allocatable
>>> -      || (sym->as && sym->as->type == AS_ASSUMED_RANK))
>>> +  /* Use the array as and attr.  */
>>> +  as = sym->as;
>>> +  array_attr = &sym->attr;
>>> +
>>> +  /* The pointer attribute is always set on a _data component, therefore
>>> check
>>> +     the sym's attribute only.  */
>>> +  if (sym->attr.pointer || array_attr->allocatable
>>> +      || (as && as->type == AS_ASSUMED_RANK))
>>>      return dummy;
>>>  
>> Any reason to sometimes use array_attr, sometimes not, like here?
>> By the way, the comment is misleading: for classes, there is the
>> class_pointer attribute (and it is a pain, I know).
> 
> Yes, and a good one. Array_attr is sometimes sym->attr and sometimes
> CLASS_DATA(sym)->attr aka sym->ts.u.derived->components->attr. In the later
> case .pointer is always set to 1 in the _data component's attr. I.e., the above
> if, would always yield true for a class_array, which is not intended, but rather
> destructive. I know about the class_pointer attribute, but I figured, that it
> is not relevant here. Any idea how to formulate the comment better, to reflect
> what I just explained?
> 
This pointer stuff is very difficult to swallow to me.
I understand that for classes, the CLASS_DATA (sym)->pointer is always
set, but almost everywhere the checks for pointerness are like
  (sym->ts.type != BT_CLASS && sym->attr.pointer)
  || (sym->ts.type == BT_CLASS && CLASS_DATA (sym)->attr.class_pointer)
and I don't see a convincing reason to have it different here.

At least gfc_is_nodesc_array should return 0 if sym->ts.type == BT_CLASS
which solves the problem there; for the other cases, I think that
class_pointer should be looked at.  gfc_build_class_symbol  clears the
sym->attr.pointer flag for class containers so it doesn't make sense to
test that flag.

Mikael