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 4 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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[–] bleistift2@sopuli.xyz 3 points 4 days ago (1 children)

If that’s the only error mechanism, sure. Exceptions in most languages tend to be relatively expensive, though, and most have a cheaper idiomatic way of returning error codes; you’d want to use those if they’re available, right?

I think not being able to get the current time from the system is very exceptional. And I think exceptional circumstances should act that way and not “look like” normal executions. To me, that means letting hell break loose, and not “silently” return a 1 instead of a 0.

By similar reasoning, “Exceptions in most languages tend to be relatively expensive” is a very weak argument. We don’t expect this error-throwing code to execute a lot.

[–] sxan@midwest.social 1 points 4 days ago

I can think if plenty of situations where system time is

  • Optional
  • Unreliable
  • And even potentially disallowed by the user

In fact, if you don't set up your containers right, the system time is almost always wrong.