OK, so people have brought up two issues: 1. It is for various reasons not recommended to call atexit() from a dynamically linked library (which Guile already does before my suggested change, n.b.).
2. It is not async signal safe. A suggested remedy would then be: Instead of calling the at-exit-hook from really_cleanup_for_exit, we could call it (still within an scm_with_guile) from the end of scm_boot_guile(), just before exit(), with the disadvantage that it wouldn't be called if main_func() calls exit on its own. It's kind of a pity that we didn't early on introduce some kind of scm_finalize_guile() which the user would have to call when done with the library... And, well, perhaps we should block asyncs, but I don't know about signals with this new setup. Best regards, Mikael On Thu, Nov 7, 2024 at 1:26 PM Mailer <vine24683...@gmail.com> wrote: > On Thu, 7 Nov 2024 12:09:25 +0000 > Mailer <vine24683...@gmail.com> wrote: > > On Thu, 7 Nov 2024 12:23:08 +0100 > > Maxime Devos <maximede...@telenet.be> wrote: > > > ‘atexit’ functions are run at ‘exit’. ‘exit’ can be run from signal > > > handlers (*). Since the hook runs Scheme code, it could do a lot of > > > AC-unsafe things, resulting in problems. > > > > > > (*) glibc documentation says ‘exit’ is AC-unsafe, but this is > > > unsupported by POSIX AFAICT. OTOH the same applies to even ‘malloc’, > > > so likely I’m looking in the wrong places. > > > > I think you meant async-signal-safe (AS-safe). 'exit' is not a-s-s and > > cannot be called in a signal handler (for example it can flush buffers) > > whereas '_exit' is a-s-s. Furthermore a registered handler cannot > > itself safely call 'exit'. > > > > I believe the main reason that use of 'atexit' or 'on_exit' is > > discouraged is that it does not handle abnormal process termination. > > (Registered handlers also don't run on termination by '_exit', but that > > is usually what you want.) > > I believe also that use of 'atexit' is discouraged in dynamically linked > libraries because of the uncertain timing of the unloading of the > library, but I think in fact glibc is OK with this, so I guess it may > depend on your libc. > > Chris > >
