9 ms·

Rust is a terrible choice. Its standard library assumes malloc never fails.

• haberman 11y ago
  This is downvoted, but I'd rather see it refuted. Is this false? Is SQLite as written tolerant of malloc() failure?
  • steveklabnik 11y ago
    The Rust standard library does assume that allocation succeeds. The language itself knows nothing about the heap, and so you can write allocators that do whatever you wish. Side note: on most Linux distros, overcommit is on, and so malloc will basically always succeed; the OOM killer will kill your program before you'd get a failure. I am less knowledgeable about OSX and Windows. I cannot speak to SQlite in this regard.
    • aidenn0 11y ago
      Even with overcommit on, malloc can return NULL on linux.
      • steveklabnik 11y ago
        liballoc does check for NULL IIRC.
    • ktRolster 11y ago
      Side note: on most Linux distros, overcommit is on, and so malloc will basically always succeed; the OOM killer will kill your program before you'd get a failure Clarifying note: this is configurable.
    • nickpsecurity 11y ago
      Holy crap, I'd never have imagined that... A design that assumes allocation always succeeds flies in the face of decades of safety/security-critical coding wisdom. I strongly recommend the team revisit and change that somehow to account for failures, NULL's, whatever. Actually, same anywhere a failure-prone, esp hardware, resource is acquired. C apps can handle this issue so Rust should as well if it's to replace them. EDIT: Thanks to replies for clarification that it's just one allocator, aborts, and others are available. Still feel weird about it but that's better.
      • kinghajj 11y ago
        Note that Rust, the language, is perfectly capable of handling memory allocation failures, it's just the standard library that makes the assumption. Embedded environments wouldn't use the standard library for numerous reasons anyway, and the "core" library uses no allocation at all. That said, IIRC handling of failure in the standard library will happen eventually, I believe there's just no consensus yet on the best way to do it.
      • tatterdemalion 11y ago
        The standard allocator will abort on oom error. For applications which need to be tolerant to oom errors, you need to use a different allocator. Most programs can't tolerate oom errors, though, and it would be absolutely unreasonable for every function in the standard library that might perform an allocation to return an error that has to be handled by every programmer all the time. EDIT: C's solution is to make it very easy to ignore oom errors, so most programmers just don't handle oom errors. Rust's solution is much better.
        • jstimpfle 11y ago
          To be fair, not a bug in the language itself. Regarding libc, it's also very easy to abort on error. Just write a function xmalloc().
        • quotemstr 11y ago
          Every function in the C++ standard library reliably communicates allocation failure to the application without relying on aborting the whole program. If Rust can do it, C++ can do it too. Rust got itself into this trap by eschewing exceptions.
          • tatterdemalion 11y ago
            Maybe avoid using judgmental language like calling a standard allocator that aborts on oom a "trap." The Rust team made conscious design choices in full awareness of the trade-offs. Moreover, Rust actually does have thread unwinding, and even the ability to catch an unwinding thread, so it is not true that the Rust standard library could not have unwound on oom. Rust's standard library just isn't designed for writing applications that need to survive oom errors. That's fine, its not designed for a number of other applications which Rust the language is well-suited for either (operating systems, for example). Its designed for the majority use case, because life is full of trade offs.
  • deleted 11y ago
    [deleted]
• sesutton 11y ago
  I'm not a Rust expert but everywhere I could find heap::allocate it checks for null.
  • rkangel 11y ago
    Any time you do Box::new() you are allocating memory. There is no way do report allocation failure from that - the program will panic.
• wyldfire 11y ago
  I suppose this coreutils impl doesn't do it but one could perhaps use rust w/o its standard library and use strictly some libc instead. Would probably still be a net win.
  • DrJokepu 11y ago
    Writing Rust code interfacing libc is a rather frustrating experience though. Many libc interfaces use constructs that Rust really wants you to avoid (for very good reasons), things such as global mutable variables (errno and for callback functions without context pointers) or union types. I know about at least one cargo crate attempting to "Rustify" libc with some level of success. None the less, this is what I typically end up doing when writing Rust code as much of th Rust standard library is simply not ready for "serious" usage.
    • ekidd 11y ago
      Personally, I rather enjoy writing clean Rust wrappers for gross C APIs. Doing so does require a solid knowledge of C, and familiarity with a small bag of Rust tricks. In my experience, the Rust standard library is extremely convenient and it handles corner cases very well. There are definitely still holes, but that's what "cargo add $CRATE_NAME" is for. My biggest annoyance with Rust (and it's not a huge one) is that if I'm doing something off the beaten path, I'm probably going to need to wrap a C library or two that nobody has wrapped yet. There's a lot of great stuff on crates.io, but it's only a minuscule fraction of the total C ecosystem.
    • pcwalton 11y ago
      > Rust code as much of th Rust standard library is simply not ready for "serious" usage. Can you elaborate on this? I've been getting serious usage out of the Rust standard library for years...
      • DrJokepu 11y ago
        There is no way to select over a range of TcpStream objects. There is no stable way to select over a range of mpsc channels. There is no way to access a TcpStream in a non-blocking manner. There is no support whatsoever for UNIX signals. I could go on.