Re: [PATCH 2/2] gdb: Resolve dynamic target types of pointers.

[Tom Tromey <tom@tromey.com>]

> Thanks for the feedback. Sorry that it took me so long to reply - the mail
> somehow got lost..

No need to apologize!  I'm constantly months behind and/or dropping email.

>> > +	  if (type->code () == TYPE_CODE_PTR && is_dynamic_type (type))
>> > +	    {
>> > +	      CORE_ADDR addr;
>> > +	      if (nullptr != TYPE_DATA_LOCATION (TYPE_TARGET_TYPE (type)))
>> > +		addr = value_address (val);
>> > +	      else
>> > +		addr = value_as_address (val);
>> 
>> This seems weird to me.  When does value_as_address fail?

> This if else has been introduced because of the way ifort/icc describe pointers
> vs. gcc/gfortran and icx/ifx.

> <1><AAA> DW_TAG_variable
>     <> DW_AT_type: <BBB>
>     <> DW_AT_location: (location of the pointer)
> <1><BBB> DW_TAG_pointer_type
>     DW_AT_type: <CCC>
> <1><CCC> DW_TAG_array_type
>     <> DW_AT_type: <DDD>
>     <> DW_AT_data_location: (location of the array)
> <2><EEE> DW_TAG_subrange_type

> Fortran:

> <1><AAA> DW_TAG_variable
>     <>   DW_AT_type: <BBB>
>     <>   DW_AT_location: (location of the pointer) 
> <1><BBB> DW_TAG_array_type
>     <> DW_AT_type: <CCC>
>     <> DW_AT_data_location: (location of the array)
> <2><DDD> DW_TAG_subrange_type

> When printing this pointer to array in gfortran/ifx the pointer print function is
> not actually called - since the DWARF does not emit a pointer here.  Instead,
> the normal array print is invoked which will use the DW_AT_data_location.
> So we do not run into this same problem

I still do not understand, sorry.

For me this looks like two different types.  In one situation, the type
is a pointer to an array.  In the second, it's just an array.  So, I
would expect them to print differently.

Are you saying these should print identically?  If so, that's fine --
but then it seems like something to do in the Fortran code, not in
c-valprint.c.

Maybe in the code the check for TYPE_DATA_LOCATION is a proxy for
checking that the pointer is a pointer to a Fortran array?  I guess I
could understand that, but it doesn't seem like a good approach, because
what if some C compiler starts emitting this?

>> I'm curious why the code added here is not also needed in f-valprint.c.

> The reason here is simply that Fortran does not have this implemented for
> Itself.  Instead the fortran f_langugage inherits from language_defn (the all
> languages base class) which simply delegates the value-print to 
> c_value_print / so changing it there suffices.

If Fortran-specific printing is needed, this will have to change.

Tom