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8103 :: Safe signal handling

[2021-06-09T19:57:22+02:00]

codic12 (orginal) [2021-06-09T19:57:22+02:00] view original

The posix.onSignal function, as well as the raw sigaction, have a very limited list of functions you can call in the handler; in particular no heap allocation is a big one. Is there any way to achieve safe signal handling in Nim without these limitations? My application has a socket server running, so what I'm thinking is to send to that but I'm not sure if Nim's net is itself async socket safe

codic12 (orginal) [2021-06-09T20:00:23+02:00] view original

Alternatives: set an atomic variable and poll that (very cpu heavy but should be 100% safe), use kqueue on BSD and signalfd on Linux

planetis (orginal) [2021-06-09T20:12:45+02:00] view original

This std/selectors maybe?

codic12 (orginal) [2021-06-09T23:05:34+02:00] view original

Looks nice, any examples of using it to handle signals?

codic12 (orginal) [2021-06-10T03:46:39+02:00] view original

I implemented the self-pipe trick, it's really easy to do for future reference, just write a byte (something like an ascii period) and spawn a thread reading the pipe. Everything you need is in posix

PMunch (orginal) [2021-06-10T08:44:36+02:00] view original

Just FYI, the reason that signal handlers shouldn't allocate on the heap is that the signal you've gotten might be an ENOMEM or similar from trying to allocate something on the heap. In this case it's simply not possible to allocate anything on the heap.