compiler/rustc_data_structures/src/flock/linux.rs

   1 //! We use `flock` rather than `fcntl` on Linux, because WSL1 does not support
   2 //! `fcntl`-style advisory locks properly (rust-lang/rust#72157). For other Unix
   3 //! targets we still use `fcntl` because it's more portable than `flock`.
   4
   5 use std::fs::{File, OpenOptions};
   6 use std::io;
   7 use std::os::unix::prelude::*;
   8 use std::path::Path;
   9
  10 #[derive(Debug)]
  11 pub struct Lock {
  12     _file: File,
  13 }
  14
  15 impl Lock {
  16     pub fn new(p: &Path, wait: bool, create: bool, exclusive: bool) -> io::Result<Lock> {
  17         let file = OpenOptions::new()
  18             .read(true)
  19             .write(true)
  20             .create(create)
  21             .mode(libc::S_IRWXU as u32)
  22             .open(p)?;
  23
  24         let mut operation = if exclusive { libc::LOCK_EX } else { libc::LOCK_SH };
  25         if !wait {
  26             operation |= libc::LOCK_NB
  27         }
  28
  29         let ret = unsafe { libc::flock(file.as_raw_fd(), operation) };
  30         if ret == -1 { Err(io::Error::last_os_error()) } else { Ok(Lock { _file: file }) }
  31     }
  32
  33     pub fn error_unsupported(err: &io::Error) -> bool {
  34         matches!(err.raw_os_error(), Some(libc::ENOTSUP) | Some(libc::ENOSYS))
  35     }
  36 }
  37
  38 // Note that we don't need a Drop impl to execute `flock(fd, LOCK_UN)`. A lock acquired by
  39 // `flock` is associated with the file descriptor and closing the file releases it
  40 // automatically.