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> They prefer slices idiomatically, but that's not "full spatial memory safety" [*] is a syntactically delineated unsafe feature. Rust has the same thing. It's

• pcwalton 4y ago
  > Rust has the same thing. In Rust all of those features are delineated by unsafe. For one, you can disable unsafe with a compiler switch; Zig has no such equivalent feature. Moreover, we shouldn't assume that Zig pointers are the only feature that breaks spatial memory safety. It was simply the first one I found after like 2 minutes of looking through the docs. After like 5 more minutes I found another: extern unions. Just now I found another: sentinel-terminated pointers, since you could delete the sentinel. It feels a bit like these arguments are going like "Zig is spatially memory safe!" "Well, what about X?" "OK, other than X, Zig is spatially memory safe!" "What about Y?" "OK, other than X and Y, Zig is spatially memory safe!" At this point the burden of proof isn't on me anymore. It's obvious that full spatial memory safety just isn't a design goal of Zig. It seems like Zig's goal is simply to add tools, like slices, that reduce memory errors. Which is the same goal that, for example, the C++ STL has. It's a great goal, but it shouldn't be confused with Rust's goal. > [1]: Even disregarding the hard question over which of Zig or Rust make it easier to write correct programs, which could go either way; that sound memory safety is a better path to correctness than a balance of less soundness combined with simplicity is your opinion It's my opinion in the same sense that it's my opinion that wearing seatbelts results in fewer deaths on the road. The idea that memory-safe programming languages improves real-world safety is backed up by decades of experience. Anyone arguing otherwise has a massive burden of proof. And the arguments I've seen by people arguing that you don't need temporal memory safety are weak. The idea that a simple language that doesn't have ironclad safety guarantees reduces errors over a more complex language with those guarantees sounds nice in theory, but it hasn't actually turned out that way in practice.
  • azakai 4y ago
    > Moreover, we shouldn't assume that Zig pointers are the only feature that breaks spatial memory safety. It was simply the first one I found after like 2 minutes of looking through the docs. After like 5 more minutes I found another: extern unions. Just now I found another: sentinel-terminated pointers, since you could delete the sentinel. You're right on each of those points. But (AFAIK) all those types are explicitly there for C interop. When interfacing with C, yes, Zig will inherit much of C's unsafety. But the big picture is that 1. Idiomatic Zig should not use those things, and 2. Those things are (IIUC) mechanically-identifiable at the type level. A compiler flag could warn about them. You can check if a codebase uses them, and find out exactly where. No such thing is possible for C. Maybe you'd prefer that an unsafe block be required to be placed around each of them, but in the end that's a matter of notation. In theory, Zig could decide to mandate such explicit unsafe blocks, but C couldn't - there isn't a useful safe subset to delineated. I could be wrong, however. Possibly the Zig community will decide that say sentinel-terminated pointers are good to use in general (and not just for C interop). And maybe I've missed something and those types cannot be discovered mechanically for auditing purposes. If either of those is the case then I'd agree Zig lacks spatial memory safety. (Btw, you seem downvoted atm. Not me, of course - there's probably no one else I respect more on the topic of memory safety than you! - and it's disappointing that people downvote comments just because they disagree.)
    • pcwalton 4y ago
      Well, let's turn this around. Is C++ spatially memory safe? C++20 has slices (ranges). They're bounds checked, via the .at() method. You can get the integer overflow semantics of Zig with "-fsanitize=signed-integer-overflow -fsanitize=unsigned-integer-overflow -fsanitize=float-cast-overflow". You could write a checker that enforces that only these features are used (in fact, this checker basically exists--ISO Core C++ Guidelines). I don't see any reason why modern C++ wouldn't be just as spatially memory safe as Zig is, if we're allowed to subset the language in ways more trivial than "disable the unsafe keyword". The main thing that distinguishes Zig at that point would be that it's a simpler language. That's true. But I don't actually think that makes for safer programs, empirically speaking--otherwise, C programs would be safer than C++ programs, and they generally aren't.
• Tozen 4y ago
  Part of the issue is that Zig is in a near category to Rust, and its areas of focus are more restricted as opposed to other general purpose and convenient to use languages. Rust already has major corporate backers and much more established popularity in the media. It can easily be seen how it can just simply overwhelm Zig, and particularly by emphasizing safety. Even if those very knowledgeable about the subject can argue to what degree safety should be the issue or is relevant with a particular project, Rust already has the hype and reputation behind it as being "safer". Zig has to make stronger and more compelling arguments as to why people should use it, instead of just reaching for Rust.