Hacker News new | ask | show | jobs
by joshkel 487 days ago
In practice, C has a couple of significant pitfalls that I've read about.

First is if you compile with `-Werror -Wall` or similar; new compiler diagnostics can result in a build failing. That's easy enough to work around.

Second, nearly any decent-sized C program has undefined behavior, and new compilers may change their handling of undefined behavior. (E.g., they may add new optimizations that detect and exploit undefined behavior that was previously benign.) See, e.g., this post by cryptologist Daniel J. Bernstein: https://groups.google.com/g/boring-crypto/c/48qa1kWignU/m/o8...
2 comments
uecker 487 days ago
Why not entirely wrong, the UB issues are bit exaggerated in my opinion. My C code from 20 years ago still works fine even when using modern compilers. In any case, our plan is to remove most of UB and there is quite good progress. Complaining that your build fails with -Werror seems a bit weird. If you do not want it, why explicitly request this with -Werror?
link
nindalf 487 days ago
Just curious, when you’re done removing all the UB, how will you know you’ve been successful? UB is hard to find isn’t it?
link
uecker 487 days ago
To be clear: I mean UB in the C standard. The cases where there is UB are mostly spelled out explicitly, so we can go through all the cases and define behavior. There might be cases where there is implicit UB, i.e. something is accidentally not specified, but this has always been fixed when noticed. It is not possible to remove all cases of UB though, but the plan is to add a memory safe mode where there is no UB similar to Rust.
link
yaro330 487 days ago
The warning argument is silly. It just means that your code is not up to par with the modern standards. -Wall is a moving goalpost and it's getting new warnings added with every release of a TC because TC developers are trying to make your code more secure.
link
joshkel 487 days ago
I mean, yeah, I said it was easy enough to work around. But it's an issue I've seen raised in a discussions of C code maintenance. (The typical conclusion is that using `-Wall -Werror` is a mistake for long-lived, not-actively-developed code.) Apologies if I overstated the case.
link