5 ms·

What are the disadvantages of using 'static here? I wonder if a garbage collected language would have a more accurate life time for that object

CyberDildonics 3y ago
You wonder based on what? Static will put something in the binary itself and it will be memory mapped in, which won't even need to be directly allocated.
- vlovich123 3y ago
  The apostrophe isn’t superfluous. ‘Static in this context refers to static lifetime. Lifetimes have absolutely 0 impact on runtime.
  - CyberDildonics 3y ago
    I'm not sure what this has to do with the parent post or how it contradicts what I said. https://doc.rust-lang.org/std/keyword.static.html https://doc.rust-lang.org/std/keyword.static.html
    - vlovich123 3y ago
      You are referring to static variables which have ‘static lifetime. OP is asking about ‘static lifetime and whether GC would somehow collect garbage more precisely (it wouldn’t). You’re basically talking past each other.
  - celeritascelery 3y ago
    How would you get a static lifetime without a static object?
    - unshavedyak 3y ago
      Unrelated to the above convo, but: An owned object can be bound by a static lifetime, for example. Eg, `fn foo<T: 'static>(t: T){}\n foo(String::new());`
      - vlovich123 3y ago
        More dangerous / less common, but you can also launder lifetimes through unsafe where you use ‘static to indicate “it’s not possible to verify lifetime at compile time but I promise you this will outlive you”. An example of this would be storing a reference that is reference counted but you don’t want the lifetime to bleed out into the type signature.
    - ben-schaaf 3y ago
      Box::leak for one.
    - remram 3y ago
      Box::leak() will make a &'static. You can also use lazy_static! to dynamically make a static global constant.
- bonzini 3y ago
  'static is a lifetime here.
vlovich123 3y ago
‘static is a compile time thing for ensuring memory safety. It doesn’t really have anything to say about when the object will be collected. In fact, since Rust/C/C++ applications use precise garbage collection techniques, they’re going to track the lifetime strictly more accurately than a garbage collected language (which I’m presuming you mean tracing GC). Of course you could have a memory leak / reference cycles but memory leaks are possible with tracing GCs as well (just different kinds of leaks but they are a strict subset of the situations that would cause a leak for things like reference counting iirc). What lifetimes do let you accomplish is more fearless ownership tracking and letting the compiler expire references for you without needing to use any kind of reference counting. And all things being equal, precise garbage tracking results in lower peak and average memory usage.

CyberDildonics 3y ago

You wonder based on what? Static will put something in the binary itself and it will be memory mapped in, which won't even need to be directly allocated.

vlovich123 3y ago
The apostrophe isn’t superfluous. ‘Static in this context refers to static lifetime. Lifetimes have absolutely 0 impact on runtime.
- CyberDildonics 3y ago
  I'm not sure what this has to do with the parent post or how it contradicts what I said. https://doc.rust-lang.org/std/keyword.static.html https://doc.rust-lang.org/std/keyword.static.html
  - vlovich123 3y ago
    You are referring to static variables which have ‘static lifetime. OP is asking about ‘static lifetime and whether GC would somehow collect garbage more precisely (it wouldn’t). You’re basically talking past each other.
- celeritascelery 3y ago
  How would you get a static lifetime without a static object?
  - unshavedyak 3y ago
    Unrelated to the above convo, but: An owned object can be bound by a static lifetime, for example. Eg, `fn foo<T: 'static>(t: T){}\n foo(String::new());`
    - vlovich123 3y ago
      More dangerous / less common, but you can also launder lifetimes through unsafe where you use ‘static to indicate “it’s not possible to verify lifetime at compile time but I promise you this will outlive you”. An example of this would be storing a reference that is reference counted but you don’t want the lifetime to bleed out into the type signature.
  - ben-schaaf 3y ago
    Box::leak for one.
  - remram 3y ago
    Box::leak() will make a &'static. You can also use lazy_static! to dynamically make a static global constant.
bonzini 3y ago
'static is a lifetime here.

vlovich123 3y ago

‘static is a compile time thing for ensuring memory safety. It doesn’t really have anything to say about when the object will be collected. In fact, since Rust/C/C++ applications use precise garbage collection techniques, they’re going to track the lifetime strictly more accurately than a garbage collected language (which I’m presuming you mean tracing GC). Of course you could have a memory leak / reference cycles but memory leaks are possible with tracing GCs as well (just different kinds of leaks but they are a strict subset of the situations that would cause a leak for things like reference counting iirc). What lifetimes do let you accomplish is more fearless ownership tracking and letting the compiler expire references for you without needing to use any kind of reference counting. And all things being equal, precise garbage tracking results in lower peak and average memory usage.