From: Eli Zaretskii <eliz@gnu.org>
To: Pip Cet <pipcet@gmail.com>
Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org
Subject: Re: master d582356: * src/fns.c (Frandom): Handle bignum `limit`s
Date: Sun, 07 Mar 2021 16:04:42 +0200 [thread overview]
Message-ID: <83a6rft5z9.fsf@gnu.org> (raw)
In-Reply-To: <CAOqdjBdw5L+h7V4LH=FHEcOStGMnOVK_koaEZ7Ktfe7p=jTxHQ@mail.gmail.com> (message from Pip Cet on Sun, 7 Mar 2021 13:27:01 +0000)
> From: Pip Cet <pipcet@gmail.com>
> Date: Sun, 7 Mar 2021 13:27:01 +0000
> Cc: Stefan Monnier <monnier@iro.umontreal.ca>, emacs-devel@gnu.org
>
> > > 1. Have FUNCTION_MAY_GC etc. translate into a GCC attribute in debug
> > > builds so we can statically check that a function that says it never
> > > calls GC doesn't call a function that says it may call GC.
> > > 2. Have a statement at the beginning of non-GCing functions which sets
> > > a flag that is then checked by garbage-collecting functions, so that
> > > we may dynamically check this.
> > >
> > > (1) seems easy to implement, but has a high rate of false negatives as
>
> "Seems". If you have a computer fast enough and enough RAM to actually
> compile emacs with -flto -fanalyzer -fdump-analyzer-json. I don't.
>
> > > many functions are safe to call from non-GCing functions as long as
> > > the arguments are correct.
> > > (2) is difficult to implement, and would only trigger at runtime.
> > >
> > > So I say we should do (1) in preference to (2), but maybe we should do both.
> >
> > I don't think I understand how will we know which function says it
> > never calls GC.
>
> By tagging it in the source code?
How do you know which functions to tag?
> > For the same reasons, I don't see how (2) can be done in practice.
>
> Sorry, I don't understand. We'd have
>
> void
> f (void)
> {
> DONT_CALL_GC ();
> g();
> }
>
> void
> g (void)
> {
> maybe_gc ();
> }
>
> and that would throw a runtime error because maybe_gc checks the flag
> set by DONT_CALL_GC.
How do you know in which functions to add DONT_CALL_GC ?
Or did you intend to add that to all the functions one by one, then
removing them as needed, until you stop getting runtime exceptions?
next prev parent reply other threads:[~2021-03-07 14:04 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210305170955.27732.27579@vcs0.savannah.gnu.org>
[not found] ` <20210305170957.AF99920E1B@vcs0.savannah.gnu.org>
2021-03-05 19:42 ` master d582356: * src/fns.c (Frandom): Handle bignum `limit`s Pip Cet
2021-03-05 19:56 ` Stefan Monnier
2021-03-05 20:13 ` Pip Cet
2021-03-05 20:34 ` Stefan Monnier
2021-03-06 7:42 ` Pip Cet
2021-03-06 8:44 ` Eli Zaretskii
2021-03-06 9:44 ` Pip Cet
2021-03-06 10:56 ` Eli Zaretskii
2021-03-06 13:22 ` Pip Cet
2021-03-06 14:45 ` Eli Zaretskii
2021-03-07 13:27 ` Pip Cet
2021-03-07 14:04 ` Eli Zaretskii [this message]
2021-03-07 14:21 ` Pip Cet
2021-03-07 15:22 ` Eli Zaretskii
2021-03-07 17:23 ` Pip Cet
2021-03-07 17:47 ` Eli Zaretskii
2021-03-07 18:37 ` Stefan Monnier
2021-03-07 19:54 ` Andrea Corallo via Emacs development discussions.
2021-03-07 19:55 ` Pip Cet
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