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I really don't understand why someone would think Rust is "pretty darn similar to C++". I think about my code and data in Rust very differently to C++. C++ does

by roca 6y ago

I really don't understand why someone would think Rust is "pretty darn similar to C++". I think about my code and data in Rust very differently to C++. C++ doesn't have tagged unions, Rust does. C++ does have inheritance, Rust doesn't. C++ templates are quite unlike Rust generics. Rust enforces safety and (mutable XOR shared), C++ doesn't. All of these lead to quite different design decisions for same-shaped problems.

pron 6y ago
You're looking at the details, while I look at the overall "feel" and find them almost indistinguishable. They're both low-level languages -- and so, like all low-level languages, suffer from low-abstraction, i.e. the difficulty to hide internal implementation details from consumers behind APIs -- that decided to invest their complexity budget to get the appearance of high-level code once you read it on the page (while the difficulty of changing it is the same as with all low-level languages), and don't hesitate to employ a fair bit of implicitness, grow a large set of features, and let compilation be slow. The details of how they do that are less important; what's most apparent is their shared design philosophy of low-level programming (although I think that Rust improves on C++ and certainly cleans it up). Zig offers a radically different approach, and one that is also radically different from C's philosophy.
- roca 6y ago
  I don't think your critiques are accurate, but anyway, the "similarity" here is that you have the same high-level critique of both languages. This does not make Rust "pretty darn similar to C++". For me, memory and data-race safety and absence of undefined behavior are critical features, but it would be misleading if I were to go around saying "C, C++ and Zig are all pretty darn similar".
  - pron 6y ago
    > the "similarity" here is that you have the same high-level critique of both languages. The similarity is that they both espouse the very same design philosophy for low-level programming. It's a pretty big similarity. > For me, memory and data-race safety and absence of undefined behavior are critical features, but it would be misleading if I were to go around saying "C, C++ and Zig are all pretty darn similar". It would be misleading, because memory safety and undefined behaviour in Zig is much closer to Rust than to C++. Even where it's not the same as Rust, it's still very different from C/C++. Safety and correctness are as emphasised in Zig as in Rust; they just go about achieving them differently. It is not clear at all which of them achieves correctness better.
    - roca 6y ago
      > Safety and correctness are as emphasised in Zig as in Rust This is so far from true I cannot take you seriously. Zig doesn't have any kind of lifetime analysis, so it's as vulnerable to use-after-free/dangling pointers as C and C++ are. That alone rules out Zig from ever being considered "memory safe" in any meaningful sense. [Yes, I'm aware of GeneralPurposeAllocator, but that is not something you want to ship in production. "Never reuse any virtual address space" is a disaster for the OS (VMA fragmentation, TLB shootdown IPIs) and the hardware (TLBs, caches). That's why no-one ships such a thing in production for C/C++. GeneralPurposeAllocator will no doubt be useful for debugging (though less effective than ASAN or Valgrind) but safety in production is the game here; ASAN doesn't make C/C++ "memory safe".] Zig also allows data races so Zig programs can have undefined behaviour via data races on non-atomic values. Again, this cannot be fixed. Even smart pointers (e.g. reference counting) are nasty in Zig. Zig doesn't have destructors so cleaning up an owning pointer or a refcounting pointer requires developers to write manual "defer" statements. Worse, these only work at function scope so you also have to write manual cleanup code for every data structure containing a smart pointer. Without idiomatic smart pointers Zig will likely be more prone to UAF bugs (and leaks) than C++.
      - pron 6y ago
        You've misunderstood. There is no doubt that Rust eliminates more undefined behaviour than Zig (though not completely), but it does it at the cost of harming other aspects of correctness. Zig does not try to eliminate UB as much as Rust, but it focuses more on reducing other types of bugs. At the end of the day, you don't care if your program fails due to UB or another bug, and it is unclear which approach results in more correct programs overall.
        roca 6y ago
        > you don't care if your program fails due to UB or another bug, Actually you do, because memory safety bugs are more likely to be exploitable than some arbitrary correctness bug, because they can be weaponized to take full control of the program. The reality is that UAF/dangling pointers are a major source of CVEs in mature software. Rust prevents those in practice, Zig doesn't. You think Zig is going to be much better than Rust at preventing other kinds of bugs. I see zero evidence of that.

by roca 6y ago

pron 6y ago

You're looking at the details, while I look at the overall "feel" and find them almost indistinguishable. They're both low-level languages -- and so, like all low-level languages, suffer from low-abstraction, i.e. the difficulty to hide internal implementation details from consumers behind APIs -- that decided to invest their complexity budget to get the appearance of high-level code once you read it on the page (while the difficulty of changing it is the same as with all low-level languages), and don't hesitate to employ a fair bit of implicitness, grow a large set of features, and let compilation be slow. The details of how they do that are less important; what's most apparent is their shared design philosophy of low-level programming (although I think that Rust improves on C++ and certainly cleans it up). Zig offers a radically different approach, and one that is also radically different from C's philosophy.

roca 6y ago
I don't think your critiques are accurate, but anyway, the "similarity" here is that you have the same high-level critique of both languages. This does not make Rust "pretty darn similar to C++". For me, memory and data-race safety and absence of undefined behavior are critical features, but it would be misleading if I were to go around saying "C, C++ and Zig are all pretty darn similar".
- pron 6y ago
  > the "similarity" here is that you have the same high-level critique of both languages. The similarity is that they both espouse the very same design philosophy for low-level programming. It's a pretty big similarity. > For me, memory and data-race safety and absence of undefined behavior are critical features, but it would be misleading if I were to go around saying "C, C++ and Zig are all pretty darn similar". It would be misleading, because memory safety and undefined behaviour in Zig is much closer to Rust than to C++. Even where it's not the same as Rust, it's still very different from C/C++. Safety and correctness are as emphasised in Zig as in Rust; they just go about achieving them differently. It is not clear at all which of them achieves correctness better.
  - roca 6y ago
    > Safety and correctness are as emphasised in Zig as in Rust This is so far from true I cannot take you seriously. Zig doesn't have any kind of lifetime analysis, so it's as vulnerable to use-after-free/dangling pointers as C and C++ are. That alone rules out Zig from ever being considered "memory safe" in any meaningful sense. [Yes, I'm aware of GeneralPurposeAllocator, but that is not something you want to ship in production. "Never reuse any virtual address space" is a disaster for the OS (VMA fragmentation, TLB shootdown IPIs) and the hardware (TLBs, caches). That's why no-one ships such a thing in production for C/C++. GeneralPurposeAllocator will no doubt be useful for debugging (though less effective than ASAN or Valgrind) but safety in production is the game here; ASAN doesn't make C/C++ "memory safe".] Zig also allows data races so Zig programs can have undefined behaviour via data races on non-atomic values. Again, this cannot be fixed. Even smart pointers (e.g. reference counting) are nasty in Zig. Zig doesn't have destructors so cleaning up an owning pointer or a refcounting pointer requires developers to write manual "defer" statements. Worse, these only work at function scope so you also have to write manual cleanup code for every data structure containing a smart pointer. Without idiomatic smart pointers Zig will likely be more prone to UAF bugs (and leaks) than C++.
    - pron 6y ago
      You've misunderstood. There is no doubt that Rust eliminates more undefined behaviour than Zig (though not completely), but it does it at the cost of harming other aspects of correctness. Zig does not try to eliminate UB as much as Rust, but it focuses more on reducing other types of bugs. At the end of the day, you don't care if your program fails due to UB or another bug, and it is unclear which approach results in more correct programs overall.
      - roca 6y ago
        > you don't care if your program fails due to UB or another bug, Actually you do, because memory safety bugs are more likely to be exploitable than some arbitrary correctness bug, because they can be weaponized to take full control of the program. The reality is that UAF/dangling pointers are a major source of CVEs in mature software. Rust prevents those in practice, Zig doesn't. You think Zig is going to be much better than Rust at preventing other kinds of bugs. I see zero evidence of that.