I found this funny.

The context is as explained by @laund@hachyderm.io

the issue is that you can’t return from inside a closure, since the closure might be called later/elsewhere

and this post was the asnwer to the question by @antonok@fosstodon.org

you got me curious what the record for the longest ? operator chain on crates.io is

Original post: https://fosstodon.org/users/antonok/statuses/111134824451525448

  • realharo
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    1 year ago

    But that’s not the case here, seeing as they have

    if self.len() >= MAX_STACK_ALLOCATION {
        return with_nix_path_allocating(self, f);
    }
    

    in the code of with_nix_path. And I think they still could’ve made it return the value instead of calling the passed in function, by using something like

    enum NixPathValue {
        Short(MaybeUninitᐸ[u8; 1024]>, usize),
        Long(CString)
    }
    
    impl NixPathValue {
        fn as_c_str(&self) -> &CStr {
            // ...
    
    impl NixPath for [u8] {
        fn to_nix_path(&self) -> ResultᐸNixPathValue> {
            // return Short(buf, self.len()) for short paths, and perform all checks here,
            // so that NixPathValue.as_c_str can then use CStr::from_bytes_with_nul_unchecked
    

    But I don’t know what performance implications that would have, and whether the difference would matter at all. Would there be an unnecessary copy? Would the compiler optimize it out? etc.

    Also, from a maintainability standpoint, the context through which the library authors need to manually ensure all the unsafe code is used correctly would be slightly larger.

    As a user of a library, I would still prefer all that over the nesting.