Author: Danny Milosavljevic <dannym@friendly-machines.com>
Date: 2026-01-25
License: ASL2.0
Subject: Use libc::flock instead of unstable std File::lock().

The file_lock feature is tracked at <https://github.com/rust-lang/rust/issues/130994>.
and is not yet stable in old Rust versions like Rust 1.85.

The file_lock feature was stabilized after Rust 1.88, but we only have 1.88.

diff -u a/codex-rs/execpolicy/Cargo.toml b/codex-rs/execpolicy/Cargo.toml
--- a/codex-rs/execpolicy/Cargo.toml
+++ b/codex-rs/execpolicy/Cargo.toml
@@ -19,6 +19,7 @@
 [dependencies]
 anyhow = { workspace = true }
 clap = { workspace = true, features = ["derive"] }
+libc = { workspace = true }
 multimap = { workspace = true }
 serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }
diff -u a/codex-rs/execpolicy/src/amend.rs b/codex-rs/execpolicy/src/amend.rs
--- a/codex-rs/execpolicy/src/amend.rs
+++ b/codex-rs/execpolicy/src/amend.rs
@@ -1,4 +1,5 @@
 use std::fs::OpenOptions;
+use std::os::unix::io::AsRawFd;
 use std::io::Read;
 use std::io::Seek;
 use std::io::SeekFrom;
@@ -100,10 +101,14 @@
             path: policy_path.to_path_buf(),
             source,
         })?;
-    file.lock().map_err(|source| AmendError::LockPolicyFile {
-        path: policy_path.to_path_buf(),
-        source,
-    })?;
+    // FIXME: Use file.lock() when Rust 1.91 is available
+    let ret = unsafe { libc::flock(file.as_raw_fd(), libc::LOCK_EX) };
+    if ret != 0 {
+        return Err(AmendError::LockPolicyFile {
+            path: policy_path.to_path_buf(),
+            source: std::io::Error::last_os_error(),
+        });
+    }

     let len = file
         .metadata()