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Change FD_SETSIZE to c_int #3356

Merged
merged 1 commit into from
Jan 8, 2024
Merged

Change FD_SETSIZE to c_int #3356

merged 1 commit into from
Jan 8, 2024

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magicant
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FD_SETSIZE defines an upper bound for file descriptors that can be added to fd_set. It is common to check if a file descriptor is less than FD_SETSIZE before adding it to an fd_set. See the example below:

fn main() {
    let path = std::ffi::CStr::from_bytes_with_nul(b"/dev/null\0").unwrap();
    let fd = unsafe { libc::open(path.as_ptr(), libc::O_RDONLY) };
    if fd < 0 {
        eprint!("open failed\n");
        return;
    }

    let mut set = std::mem::MaybeUninit::<libc::fd_set>::uninit();
    unsafe { libc::FD_ZERO(set.as_mut_ptr()) }
    if fd < libc::FD_SETSIZE { // <- type mismatch!
        unsafe { libc::FD_SET(fd, set.as_mut_ptr()) }
    } else {
        eprint!("too large fd\n");
    }
}

Unfortunately, this example does not compile because of a type mismatch. fd is c_int while FD_SETSIZE is usize (or size_t).
Since FD_SETSIZE represents the max file descriptor + 1, I think it should have the same type as file descriptors. This pull request modifies the type to c_int and adds casts where needed.

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rustbot commented Sep 18, 2023

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @JohnTitor (or someone else) soon.

Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (S-waiting-on-review and S-waiting-on-author) stays updated, invoking these commands when appropriate:

  • @rustbot author: the review is finished, PR author should check the comments and take action accordingly
  • @rustbot review: the author is ready for a review, this PR will be queued again in the reviewer's queue

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rustbot commented Sep 18, 2023

Some changes occurred in solarish module

cc @jclulow, @pfmooney

Some changes occurred in OpenBSD module

cc @semarie

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bors commented Sep 21, 2023

☔ The latest upstream changes (presumably #3348) made this pull request unmergeable. Please resolve the merge conflicts.

@sthibaul
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sthibaul commented Nov 9, 2023

Please also update src/unix/hurd/mod.rs, introduced in the meanwhile, thanks!

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magicant commented Nov 9, 2023

Rebased and updated my commit.

I also changed _POSIX_OPEN_MAX as well as _POSIX_FD_SETSIZE to c_int since the latter is defined as an alias of the former.

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bors commented Nov 9, 2023

☔ The latest upstream changes (presumably #3428) made this pull request unmergeable. Please resolve the merge conflicts.

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sthibaul commented Nov 9, 2023

Ah, sorry, my commit indeed modified a lot, up to conflicting yours.

@magicant
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No problem, my diff is so small that the conflict can be easily resolved 🙂

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@bors r+

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bors commented Jan 8, 2024

📌 Commit 500365e has been approved by JohnTitor

It is now in the queue for this repository.

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bors commented Jan 8, 2024

⌛ Testing commit 500365e with merge 7412a8b...

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bors commented Jan 8, 2024

☀️ Test successful - checks-actions, checks-cirrus-freebsd-13, checks-cirrus-freebsd-14
Approved by: JohnTitor
Pushing 7412a8b to main...

@bors bors merged commit 7412a8b into rust-lang:main Jan 8, 2024
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@asomers asomers mentioned this pull request Mar 22, 2024
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@magicant magicant deleted the fd_setsize_type branch March 24, 2024 04:01
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