refactor(fspy): own macOS shared-memory mapping

Co-authored-by: GPT-5.6 <gpt-5.6@openai.com>

Author: wan9chi

Cargo.lock

@@ -122,7 +122,6 @@ serde = "1.0.219"
 serde_json = "1.0.140"
 serde_norway = "0.9.42"
 sha2 = "0.11.0"
-shared_memory = "0.12.4"
 shell-escape = "0.1.5"
 similar = "3.0.0"
 smallvec = { version = "2.0.0-alpha.12", features = ["std"] }

Cargo.toml

@@ -140,7 +140,7 @@ impl Deref for Sender {
 }
 
 #[cfg_attr(
-    not(target_os = "linux"),
+    target_os = "windows",
     expect(
         clippy::non_send_fields_in_send_ty,
         reason = "`Sender` holds a shared file lock that ensures there's no reader, so `shm` can be safely written to"
@@ -161,7 +161,7 @@ pub struct Receiver {
 }
 
 #[cfg_attr(
-    not(target_os = "linux"),
+    target_os = "windows",
     expect(
         clippy::non_send_fields_in_send_ty,
         reason = "Receiver doesn't read or write `shm`. It only passes it to `ReceiverLockGuard` under the lock"

crates/fspy_shared/src/ipc/channel/mod.rs

@@ -7,9 +7,6 @@ license.workspace = true
 publish = false
 rust-version.workspace = true
 
-[target.'cfg(not(any(target_os = "linux", target_os = "windows")))'.dependencies]
-shared_memory = { workspace = true, features = ["logging"] }
-
 [target.'cfg(target_os = "linux")'.dependencies]
 base64 = { workspace = true }
 memmap2 = { workspace = true }
@@ -18,6 +15,11 @@ tempfile = { workspace = true }
 tokio = { workspace = true, features = ["macros", "net", "rt", "sync", "time"] }
 uuid = { workspace = true, features = ["v4"] }
 
+[target.'cfg(target_os = "macos")'.dependencies]
+memmap2 = { workspace = true }
+rustix = { workspace = true, features = ["fs", "param", "shm"] }
+uuid = { workspace = true, features = ["v4"] }
+
 [target.'cfg(target_os = "windows")'.dependencies]
 uuid = { workspace = true, features = ["v4"] }
 windows-sys = { workspace = true, features = [

crates/fspy_shm/Cargo.toml

@@ -1,92 +1,21 @@
 //! Platform shared-memory implementation for fspy channels.
 
-#[cfg(not(any(target_os = "linux", target_os = "windows")))]
-use std::io;
-
 #[cfg(target_os = "linux")]
 mod linux;
+#[cfg(target_os = "macos")]
+mod macos;
 #[cfg(target_os = "windows")]
 mod windows;
 
 #[cfg(target_os = "linux")]
 pub use linux::{CreatedShm, Shm, ShmBroker, ShmBrokerHandle, create, open};
-#[cfg(not(any(target_os = "linux", target_os = "windows")))]
-use shared_memory::{Shmem, ShmemConf};
+#[cfg(target_os = "macos")]
+pub use macos::{CreatedShm, Shm, create, open};
 #[cfg(target_os = "windows")]
 pub use windows::{CreatedShm, Shm, create, open};
 
-/// An owned shared-memory mapping.
-#[cfg(not(any(target_os = "linux", target_os = "windows")))]
-pub struct Shm {
-    inner: Shmem,
-}
-
-/// A newly created shared-memory mapping and its platform service.
-#[cfg(not(any(target_os = "linux", target_os = "windows")))]
-pub struct CreatedShm {
-    /// The owned shared-memory mapping.
-    pub shm: Shm,
-}
-
-/// Creates a shared-memory mapping of `size` bytes.
-///
-/// # Errors
-///
-/// Returns an error if the platform cannot create or map the region.
-#[cfg(not(any(target_os = "linux", target_os = "windows")))]
-pub fn create(size: usize) -> io::Result<CreatedShm> {
-    let conf = ShmemConf::new().size(size);
-
-    let inner = conf.create().map_err(io::Error::other)?;
-    Ok(CreatedShm { shm: Shm { inner } })
-}
-
-/// Opens the shared-memory mapping identified by `id`.
-///
-/// # Errors
-///
-/// Returns an error if the mapping does not exist or cannot be mapped.
-#[cfg(not(any(target_os = "linux", target_os = "windows")))]
-pub fn open(id: &str, size: usize) -> io::Result<Shm> {
-    let conf = ShmemConf::new().size(size).os_id(id);
-
-    let inner = conf.open().map_err(io::Error::other)?;
-    Ok(Shm { inner })
-}
-
-#[cfg(not(any(target_os = "linux", target_os = "windows")))]
-#[expect(clippy::len_without_is_empty, reason = "shared-memory mappings are always non-empty")]
-impl Shm {
-    /// Returns this mapping's opaque platform identifier.
-    #[must_use]
-    pub fn id(&self) -> &str {
-        self.inner.get_os_id()
-    }
-
-    /// Returns the mapped length in bytes.
-    #[must_use]
-    pub fn len(&self) -> usize {
-        self.inner.len()
-    }
-
-    /// Returns a raw pointer to the first mapped byte.
-    #[must_use]
-    pub fn as_ptr(&self) -> *mut u8 {
-        self.inner.as_ptr()
-    }
-
-    /// Returns the mapped bytes as a shared slice.
-    ///
-    /// # Safety
-    ///
-    /// The caller must ensure that no process or thread mutates the mapping for
-    /// the lifetime of the returned slice.
-    #[must_use]
-    pub unsafe fn as_slice(&self) -> &[u8] {
-        // SAFETY: The caller upholds the same synchronization contract required by `Shmem`.
-        unsafe { self.inner.as_slice() }
-    }
-}
+#[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
+compile_error!("fspy_shm does not support this platform");
 
 #[cfg(test)]
 mod tests {