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It can’t stop me from accessing index 1 when I meant 0 on a 3d array, so I think the claim doesn’t make much sense. Rust can stop me from accessing index N+1 th
by atty 4y ago
It can’t stop me from accessing index 1 when I meant 0 on a 3d array, so I think the claim doesn’t make much sense. Rust can stop me from accessing index N+1 though, which is useful for security. Of course almost every language also has support for bounds checked arrays either in their core or their standard library, and some for of array iterators, so I don’t think that’s a particularly compelling reason to choose Rust.
- cmeacham98 4y agoWhat are the bounds checked arrays in C's or C++'s standard library?
- haolez 4y agoYou can enable bound checking when calling the compiler. I don't remember the actual command line flags, though.
- cmeacham98 4y agoA non-standard compiler feature is not "their core or their standard library".
- pjmlp 4y agoThe ISO standard requires at() to be checked, while it leaves for implementations the freedom to decide if operator[]() is checked or not. As such, checks for operator[]() are usually only enabled in debug builds, although Android and Red-Hat ship with them enabled into production. Additionally, before C++ got a standard library, the frameworks that were shipped alongside compilers always had those checks enabled by default.
- ablatner 4y agostd::vector, with dynamic memory allocation, is not necessarily safe for embedded applications. It seems like Rust provides bounds checks at a primitive level.
- cmeacham98 4y agoI'll admit I don't have the stats in front of me, but I can practically for guarantee code using std::vector in the wild that [] usage outnumbers .at() usage, probably at least 10 (or even 100) to 1. C also doesn't have .at(). Considering C and C++ are the most obvious and direct competitors to Rust, bounds checking would be a significant upgrade if Rust paradigms cause it to be used more often.
- pjmlp 4y agoIt does, but as I mentioned, Red-Hat and Android ship with bounds checking enabled via FORTIFY. C was already a bad option in the mid-90's compared with the alternatives, it is due to the unfortunate adoption of GNU manifesto and POSIX systems that we got where we are. Hence why the ultimate solution is to have hardware memory tagging for bounds checking, Solaris has been doing it for a decade, ARM is following along, including a collaboration with CHERI, only Intel borked their MPX design, and it seems not to be on RISC-V's radar. Note that while defaults matter, and given the option one should rather use a safe systems language, if there are ways to do unbound accesses, there will always be some folks going that route because reasons.
- cmeacham98 4y ago> It does, but as I mentioned, Red-Hat and Android ship with bounds checking enabled via FORTIFY. I was under the impression FORTIFY only checked bounds with specific functions (mostly those starting with "mem" or "str"), and not on general pointer arithmetic. Thus, an OOB array access would not be caught. Am I wrong on this? Online sources seem to agree with my understanding: https://zatoichi-engineer.github.io/2017/10/06/fortify-source.html https://zatoichi-engineer.github.io/2017/10/06/fortify-sourc... Additionally, FORTIFY does not work on variable length arrays (like std::vector), only those which have a size known at compile time. > Hence why the ultimate solution is to have hardware memory tagging for bounds checking, Solaris has been doing it for a decade, ARM is following along, including a collaboration with CHERI, only Intel borked their MPX design, and it seems not to be on RISC-V's radar. Unfortunately, Intel and ARM are the only relevant vendors here (at least in 2022, but for the record I wish the others the best of luck), so Intel's implementation sucking is a huge blow.