I remember people being so excited to use error values instead of exceptions in mainstream languages. But this libraries plus error values combo looks even more complex to me.
But in languages with exceptions, if you want to know how a function can fail, you have two options:
- Hope the documentation is correct (it isn’t)
- Read the body of the function and every function it calls
Reasonable people can disagree on the right approach here, but I know which I prefer.
Or maybe you have 100% path coverage in your test..
Knowing what kind of errors can occur is one of those tools.
But often some "expected" errors can be handled in some way better (retry, ask user, use alternate approach, ...)
Almost every function can fail with OutOfMemoryError and you can't do anything about it.
I've accepted that everything can fail. Just write code and expect it to throw. Write programs and expect them to abort.
I don't understand this obsession with error values. I remember when C++ designers claimed, that exceptions provide faster code execution for happy path, so even for systems language they should be preferred. Go error handling is bad. Rust error handling is bad. C error handling is bad, but at least that's understandable.
> Almost every function can fail with OutOfMemoryError and you can't do anything about it.
In fact we can - though rarely do - prove software does not have either of these mistakes. We can bound stack usage via analysis, we usually don't but it's possible.
And avoiding OOM is such a widespread concern that Rust-for-Linux deliberately makes all allocating calls explicitly fallible or offers strategies like Vec::push_within_capacity a method which, if it succeeds pushes the object into the collection, but, if it's full rather than allocate (which might fail) it gives back the object - no, you take it.
Why? Let's say you've opened a memory mapped file, you've got pointer, and hand this pointer down to some library - "Here work there" - the library thinks - oh, it's normal memory - fine! And then - physical block error happens (whether it's Windows, OSX, Linux, etc.) - and now you have to handle this from... a rather large distance - where "error code" handling is not enough - and you have to use signal handling with SIGxxx or Windows SEH handling, or whatever the OS provides
And then you have languages like GoLang/Rust/others where this is a pain point (yes you can handle it), but how well?
If you look in ReactOS the code is full with `__try/__except` - https://github.com/search?q=repo%3Areactos%2Freactos+_SEH2_T... - because user provided memory HAVE to be checked - you don't want exception happening at the kernel reading bad user memory.
So it's all good and fine, until you have to face this problem... Or decide to not use mmap files (is this even possible?).
Okay, I know it's just a silly little thing I'm pointing here - but I don't know of any good solution off hand...
And even handling this in C/C++ with all SEH capabilities - it still sucks...
In user-space, memory overcommit means that we will almost or literally never see an out of memory error.
In kernel space and other constrained environments, we can simply check for allocation, failure and handle it accordingly.
This is a terrible argument for treating all code as potentially failing with any possible error condition.
Only if you control the entire ecosystem, from application to every library you're ever going to use. And will not work for library code anyway.
> In user-space, memory overcommit means that we will almost or literally never see an out of memory error.
Have you ever deployed an application to production? Where it runs in the container, with memory limits. Or just good old ulimit. Or any language with VM or GC which provides explicit knobs to limit heap size (and these knobs are actually used by deployers).
> This is a terrible argument for treating all code as potentially failing with any possible error condition.
This is reality. Some programs can ignore it, hand-waving possibilities out, expecting that it won't happen and it's not your problem. That's one approach, I guess.
Two edge cases existing is a terrible argument for creating a world in which any possible edge case must also be accounted for.
>> This is a terrible argument for treating all code as potentially failing with any possible error condition.
> This is reality. Some programs can ignore it, hand-waving possibilities out, expecting that it won't happen and it's not your problem. That's one approach, I guess.
No, it’s not reality. It’s the mess you create when you work in languages with untyped exception handling and with people that insist on writing code the way you suggest.
I'm not talking about embedded or kernels. Different stories.
real
compared to every exception-based language I’ve used, rust error handling is a dream. my one complaint is async, but tbh I don’t think exceptions would fare much better since things like the actor model just don’t really support error propagation in any meaningful way
But the best so far method I know.
I'm not trying to defend exceptions, nor checked ones, just trying to point out that I don't think they are the same.
For all intent and purposes I really liked Common Lisp's exception handling, in my opinion the perfect one ("restartable"), but it also comes with lots of runtime efficiency (and possibly other) cost (interoperability? safety (nowadays)...) - but it was valiant effort to make programmer better - e.g. iterate while developing, and while it's throwing exceptions at you, you keep writing/updating the code (while it's running), etc - probably not something modern day SRE/devops would want (heh "who taught live updating of code of running system is great idea :)" - I still do, but I can see someone from devops frowning - "This is not the version I've pushed"...)
It warns you if you ignore handling a Result because the type is annotated with must_use (which can be a compile error in CI if you choose to enforce 0 warnings). Not that this is true with try/catch - no one forces you to actually do anything with the error.
> What about errors (results) that came from deeper?
Same as with exceptions - either you handle it or propagate it up or ignore it.
Not to mention Rust also allocates dynamic objects on the heap. So not sure what is your point.
My point is runtime overhead. In C# structs and their refs (including a simple borrow checker to detect invalid ref use) were introduced to escape GC management und reduce it's runtime impact on the programs