Re: [Patch, fortran] PR37336 finalization

[Tobias Burnus <tobias@codesourcery.com>]

On 08.03.23 16:12, Steve Kargl via Fortran wrote:
> For one of my codes, I see
> % foreach i (*.o)
> foreach? nm $i | grep final
> foreach? end
> 0000000000000280 T __beamsm_MOD___final_beamsm_Table_t
> 0000000000000580 T __bsam_MOD___final_bsam_Bsa_info_t
> 00000000000001e0 T __bsam_MOD___final_bsam_Bsa_t
> 00000000000000a0 T __ffn_data_MOD___final_ffn_data_Fe_t
>
> I do not explicitly use finalization nor do I have
> subprograms named __final_*.  To me, this re-inforces
> Richard's point about not breaking existing code.

I think there are two places where finalization is touched: (a) when
declaring a type, finalization procedures might get generated.(*) — And,
(b) invoking finalization procedures.

(a) happens if you have you explicitly add finalization functions – or
(I believe) when you have allocatable components as GCC may then need to
free them.

I think (b) only happens if you either have polymorphism (as then you
don't know whether the polymorphic function uses finalization) – or when
you invoke explicitly finalization.

I believe you run into (a) – the finalization generation. My
understanding is that Paul's patch is mostly about (b) and for sure not
for the default-generated procedures. But of course, any code one
touches for one purpose can still have side effects, affecting seemingly
unrelated code.

Tobias

PS: I think we should change at some point when the virtual tables and
their default procs (init, copy, finalize) generated.

Namely, instead of generating them for all types – even if not used – it
makes sense to generate them only when a type is used in CLASS(t). This
will lead to the generation in multiple translation units, but weak
symbols come to a rescue – and for a MODULE, it can be stored in the
.mod file that the vtable + funcs has been generated. That way, way
fewer vtables are generated, saving a lot of space and reducing compile
time!

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