this post was submitted on 04 Aug 2025
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Programming

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Handling of unlikely syscall errors (programming.dev)
submitted 3 days ago by hades@programming.dev to c/programming@programming.dev
14 comments fedilink hide all child comments
 

If you were designing a standard library of a high level language (like Rust, C++, etc.) what would it do if while getting the current time of day (e.g. SystemTime::now()) it encountered a failed kernel system call (e.g. to clock_gettime) and why?

What do you think the existing implementations do?

  • Return error or raise exception
  • Return 0
  • Return undefined values (like stack garbage)
  • Panic/crash/segfault
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[โ€“] anton@lemmy.blahaj.zone 2 points 3 days ago (1 children)

I think you should make the overwhelmingly likely case crash in a controlled way, but provide a way to handle it for people who truly want to keep going in such strange conditions.

In rust I would panic in now(), but also provide a alternative call that returns a result named something like try_now(), similar to Vec::with_capacity and Vec::try_with_capacity.
In languages that provide them, you could also throw a runtime exception that can be ignored and just bubbles up to main unless explicitly caught.

[โ€“] hades@programming.dev 4 points 3 days ago

Interestingly, Rust is what brought me to this rabbit hole. It does indeed panic in now()[1], but the devs seem to be reluctant to provide the try_now() variant[2].

[1] https://doc.rust-lang.org/nightly/src/std/sys/pal/unix/time.rs.html#124 [2] https://github.com/rust-lang/rust/issues/115482