upvote

points

by nh22 hours ago |
comments
upvoteby jppittma1 hours ago|
next
[-]
C has unions. C has sum types. People have been doing tagged unions in C for longer than rust has been a language
reply
upvoteby K0nserv1 hours ago|
parent|
next
[-]
I don't think I've ever seen a C function that uses unions for this purpose though?

I can think of two common patterns that I've seen frequently:

* Return NULL for errors (sometimes with a global errorno() function).

* Return an integer error with any return values as out parameters.

So if it is possible to improve, why doesn't anyone do it?

reply
upvoteby aliceryhl1 hours ago|
parent|
prev|
[-]
Yet the authors of crypt did not use them. The C language is not designed in a way to encourage people to write code that correctly uses tagged unions (or nullable pointers for that matter).
reply
upvoteby jppittma58 minutes ago|
parent|
[-]
Where are you going with those goal posts?
reply
upvoteby rini172 minutes ago|
parent|
next
[-]
Goalposts are fine. If crypt did return union type, C still allows cowboy programmers to straight extract the char* without any check whether it's valid. So we'd end up in exactly the same situation.
reply
upvoteby Philpax12 minutes ago|
parent|
prev|
[-]
Nowhere. It's the same argument as upthread. A language that forces downstream consumers of an API to correctly deal with all possible outcomes would have prevented this.
reply
upvoteby dolmen54 minutes ago|
prev|
next
[-]
Nope.

Because in fact all the changes were about changing the function signatures. The function signature is enforced by the linker. The semantic of strings that go through isn't.

Returning 2 values is possible in C (via pointers input parameters). The main issue here is that libc is a strong API contract based on C function signatures, that nobody can change, only augment with new symbols. Such strong API compatibility constraints happen in any programming language, and workaround to fit new behaviours in old APIs happens everywhere.

reply
upvoteby K0nserv20 minutes ago|
parent|
[-]
I don't think nh2 is saying that this is how the "issue" should've been solved here, but that it's a fatal flaw of C itself (yes I know, unions, but no one uses them).

But also, its not like there were many alternative languages when the POSIX standards were designed so it's fair that it works like this.

reply
upvoteby 2 hours ago|
prev|
[-]
deleted
reply