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Zig doesn't propose to prevent UB (in fact the docs say that it takes aggressive advantage of it for optimization). (Neither does Rust.)

by jibalt 5y ago

tialaramex 5y ago
safe Rust doesn't have any Undefined Behaviour. Your unsafe Rust is supposed to provide suitable constraint/ guarantees that you, the programmer, conclude it does not have any Undefined Behaviour. The language can't force you to do this, and at some point it becomes a social contract not a programming language feature. I wrote the misfortunate crate to explore Rust's promise here. The crate provides legal but obviously inappropriate implementations of lots of safe Rust traits, and sure enough nothing blows up, there is no undefined behaviour. The defined behaviour can be undesirable for example if you insist on putting a bunch of misfortunate::Maxwells in a HashSet you're going to have a bad time. Rust doesn't promise this is a good idea, it might cause infinite loops, memory leaks, all sorts of defined trouble, but it won't be Undefined Behaviour.
- jibalt 5y ago
  Not "you, the programmer", any programmer. The Rust standard library can and sometimes does have UB, and that's even more true for other libraries.
  - tialaramex 5y ago
    "This software may have bugs" seems like a very different situation from "Our language just doesn't care whether maybe your program is nonsense and might have Undefined Behaviour".
    - jibalt 5y ago
      Nice strawman and goalpost shifting. You said that it's up to "you", the programmer, whether unsafe code misbehaves, but this simply isn't true because "you" don't control all the unsafe code you execute. Again, third party libraries can have UB ... that it's wrapped in "unsafe" keywords doesn't change that, it just means that the compiler offers a tool to help reduce it. What I said is that rust doesn't propose to prevent UB, and that's true. I didn't say that it doesn't care. (And it's not true that Zig doesn't care, either, but it makes a different tradeoff between intrusive limitations and safety.)

Zig doesn't propose to prevent UB (in fact the docs say that it takes aggressive advantage of it for optimization). (Neither does Rust.)

by jibalt 5y ago

Zig doesn't propose to prevent UB (in fact the docs say that it takes aggressive advantage of it for optimization). (Neither does Rust.)

tialaramex 5y ago

safe Rust doesn't have any Undefined Behaviour. Your unsafe Rust is supposed to provide suitable constraint/ guarantees that you, the programmer, conclude it does not have any Undefined Behaviour. The language can't force you to do this, and at some point it becomes a social contract not a programming language feature. I wrote the misfortunate crate to explore Rust's promise here. The crate provides legal but obviously inappropriate implementations of lots of safe Rust traits, and sure enough nothing blows up, there is no undefined behaviour. The defined behaviour can be undesirable for example if you insist on putting a bunch of misfortunate::Maxwells in a HashSet you're going to have a bad time. Rust doesn't promise this is a good idea, it might cause infinite loops, memory leaks, all sorts of defined trouble, but it won't be Undefined Behaviour.

jibalt 5y ago
Not "you, the programmer", any programmer. The Rust standard library can and sometimes does have UB, and that's even more true for other libraries.
- tialaramex 5y ago
  "This software may have bugs" seems like a very different situation from "Our language just doesn't care whether maybe your program is nonsense and might have Undefined Behaviour".
  - jibalt 5y ago
    Nice strawman and goalpost shifting. You said that it's up to "you", the programmer, whether unsafe code misbehaves, but this simply isn't true because "you" don't control all the unsafe code you execute. Again, third party libraries can have UB ... that it's wrapped in "unsafe" keywords doesn't change that, it just means that the compiler offers a tool to help reduce it. What I said is that rust doesn't propose to prevent UB, and that's true. I didn't say that it doesn't care. (And it's not true that Zig doesn't care, either, but it makes a different tradeoff between intrusive limitations and safety.)