Deprecate old shared memory fd creation (#374)

* deprecate shm_open

* fixing dangling references to removed memfd feature

.github/workflows/main.yml

@@ -23,13 +23,6 @@ jobs:
           - { target: x86_64-pc-windows-msvc, os: windows-latest }
           - { target: i686-pc-windows-msvc, os: windows-latest }
         features: ["", "force-inprocess", "async"]
-        include:
-          - features: ""
-            platform: { target: x86_64-pc-windows-msvc, os: windows-latest }
-          - features: ""
-            platform: { target: i686-pc-windows-msvc, os: windows-latest }
-          - features: "memfd"
-            platform: { target: x86_64-unknown-linux-gnu, os: ubuntu-latest }
     steps:
       - uses: actions/checkout@v4
 

Cargo.toml

@@ -26,7 +26,6 @@ harness = false
 [features]
 default = []
 force-inprocess = []
-memfd = []
 async = ["futures", "futures-test"]
 win32-trace = []
 

src/lib.rs

@@ -19,32 +19,21 @@
 //! The `inprocess` backend is a dummy back-end, that behaves like the real ones,
 //! but doesn't actually work between processes.
 //!
-//! ## `memfd`
-//!
-//! Use [memfd_create] to back [OsIpcSharedMemory] on Linux. [memfd_create] was
-//! introduced in kernel version 3.17. __WARNING:__ Enabling this feature with kernel
-//! version less than 3.17 will cause panics on any use of [IpcSharedMemory].
-//!
 //! ## `unstable`
 //!
 //! [IpcReceiver]: ipc/struct.IpcReceiver.html
 //! [IpcSender]: ipc/struct.IpcSender.html
 //! [IpcReceiverSet]: ipc/struct.IpcReceiverSet.html
 //! [IpcSharedMemory]: ipc/struct.IpcSharedMemory.html
 //! [OsIpcSharedMemory]: platform/struct.OsIpcSharedMemory.html
-//! [memfd_create]: http://man7.org/linux/man-pages/man2/memfd_create.2.html
 
 #[cfg(any(
     feature = "force-inprocess",
     target_os = "windows",
     target_os = "android",
     target_os = "ios"
 ))]
-#[cfg(all(
-    feature = "memfd",
-    not(feature = "force-inprocess"),
-    target_os = "linux"
-))]
+#[cfg(all(not(feature = "force-inprocess"), target_os = "linux"))]
 #[cfg(feature = "async")]
 use futures;
 

src/platform/unix/mod.rs

@@ -1120,29 +1120,11 @@ fn new_msghdr(iovec: &mut [iovec], cmsg_buffer: *mut cmsghdr, cmsg_space: MsgCon
     msghdr
 }
 
-#[cfg(not(all(target_os = "linux", feature = "memfd")))]
-fn create_shmem(name: CString, length: usize) -> c_int {
-    unsafe {
-        // NB: the FreeBSD man page for shm_unlink states that it requires
-        // write permissions, but testing shows that read-write is required.
-        let fd = libc::shm_open(
-            name.as_ptr(),
-            libc::O_CREAT | libc::O_RDWR | libc::O_EXCL,
-            0o600,
-        );
-        assert!(fd >= 0);
-        assert!(libc::shm_unlink(name.as_ptr()) == 0);
-        assert!(libc::ftruncate(fd, length as off_t) == 0);
-        fd
-    }
-}
-
-#[cfg(all(feature = "memfd", target_os = "linux"))]
 fn create_shmem(name: CString, length: usize) -> c_int {
     unsafe {
         let fd = libc::memfd_create(name.as_ptr(), libc::MFD_CLOEXEC);
         assert!(fd >= 0);
-        assert!(libc::ftruncate(fd, length as off_t) == 0);
+        assert_eq!(libc::ftruncate(fd, length as off_t), 0);
         fd
     }
 }