Use a wrapper type implementing Sync, instead of static mut (#700)

* Use a wrapper type implementing `Sync`, instead of `static mut`

`static mut` is generally best avoided. It seems to only be necessary
currently to allow the use of non-`Sync` types, since pointers are not
sync.

This also removes the `NULLPTR` constant in favor of using
`std::ptr::null`, uses `.as_ptr()` instead of casting, and uses the
arrray repeating syntax to define `types_null`. None of those should
impact behavior or the public API.

`*_requests` and `*_events` static are no longer public now. This is
theoretically a breaking change, but shouldn't really impact anything.

* Suppress `clippy::test_attr_in_doctest` lint

* Address nightly warnings

wayland-backend/src/rs/client_impl/mod.rs

@@ -28,8 +28,6 @@ use super::{
     wire::MessageParseError,
 };
 
-pub use crate::types::client::{InvalidId, NoWaylandLib, WaylandError};
-
 #[derive(Debug, Clone)]
 struct Data {
     client_destroyed: bool,
@@ -407,7 +405,7 @@ impl InnerBackend {
         // Prepare the message in a debug-compatible way
         let args = args.into_iter().map(|arg| {
             if let Argument::NewId(ObjectId { id: p }) = arg {
-                if !p.id == 0 {
+                if p.id != 0 {
                     panic!("The newid provided when sending request {}@{}.{} is not a placeholder.", object.interface.name, id.id, message_desc.name);
                 }
                 if let Some((child_id, child_serial, child_interface)) = child {

wayland-backend/src/rs/wire.rs

@@ -1,7 +1,6 @@
 //! Types and routines used to manipulate arguments from the wire format
 
 use std::collections::VecDeque;
-use std::convert::TryInto;
 use std::ffi::CStr;
 use std::os::unix::io::RawFd;
 use std::os::unix::io::{BorrowedFd, OwnedFd};

wayland-backend/src/sys/client_impl/mod.rs

@@ -29,8 +29,6 @@ use smallvec::SmallVec;
 
 use wayland_sys::{client::*, common::*, ffi_dispatch};
 
-pub use crate::types::client::{InvalidId, NoWaylandLib, WaylandError};
-
 use super::{free_arrays, RUST_MANAGED};
 
 use super::client::*;

wayland-backend/src/sys/server_impl/mod.rs

@@ -25,6 +25,7 @@ use wayland_sys::{common::*, ffi_dispatch, server::*};
 
 use super::{free_arrays, server::*, RUST_MANAGED};
 
+#[allow(unused_imports)]
 pub use crate::types::server::{Credentials, DisconnectReason, GlobalInfo, InitError, InvalidId};
 
 scoped_thread_local! {

wayland-backend/tests/rs_sys_impls.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::test_attr_in_doctest)]
+
 //! Tests to ensure the rust and sys types implement the same traits.
 
 /// A macro used to assert a type defined in both the rust and sys implementations of wayland-backend

wayland-scanner/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Use wrapper type implementing `Sync` instead of `static mut`s.
+
 ## 0.31.1 -- 2024-01-29
 
 - Include an `std::convert::Infallible` in hidden `__phantom_lifetime` enum variants,

wayland-scanner/src/c_interfaces.rs

@@ -1,5 +1,4 @@
 use std::cmp;
-use std::iter::repeat;
 
 use proc_macro2::{Literal, TokenStream};
 use quote::{format_ident, quote};
@@ -27,14 +26,13 @@ pub(crate) fn generate_interfaces_prefix(protocol: &Protocol) -> TokenStream {
 
     let types_null_len = Literal::usize_unsuffixed(longest_nulls);
 
-    let nulls = repeat(quote! { NULLPTR as *const wayland_backend::protocol::wl_interface })
-        .take(longest_nulls);
-
     quote! {
-        const NULLPTR: *const std::os::raw::c_void = 0 as *const std::os::raw::c_void;
-        static mut types_null: [*const wayland_backend::protocol::wl_interface; #types_null_len] = [
-            #(#nulls,)*
-        ];
+        use std::ptr::null;
+        struct SyncWrapper<T>(T);
+        unsafe impl<T> Sync for SyncWrapper<T> {}
+        static types_null: SyncWrapper<[*const wayland_backend::protocol::wl_interface; #types_null_len]> = SyncWrapper([
+            null::<wayland_backend::protocol::wl_interface>(); #types_null_len
+        ]);
     }
 }
 
@@ -47,24 +45,24 @@ pub(crate) fn generate_interface(interface: &Interface) -> TokenStream {
     let version_value = Literal::i32_unsuffixed(interface.version as i32);
     let request_count_value = Literal::i32_unsuffixed(interface.requests.len() as i32);
     let requests_value = if interface.requests.is_empty() {
-        quote! { NULLPTR as *const wayland_backend::protocol::wl_message }
+        quote! { null::<wayland_backend::protocol::wl_message>() }
     } else {
         let requests_ident = format_ident!("{}_requests", interface.name);
-        quote! { unsafe { &#requests_ident as *const _ } }
+        quote! { #requests_ident.0.as_ptr() }
     };
     let event_count_value = Literal::i32_unsuffixed(interface.events.len() as i32);
     let events_value = if interface.events.is_empty() {
-        quote! { NULLPTR as *const wayland_backend::protocol::wl_message }
+        quote! { null::<wayland_backend::protocol::wl_message>() }
     } else {
         let events_ident = format_ident!("{}_events", interface.name);
-        quote! { unsafe { &#events_ident as *const _ } }
+        quote! { #events_ident.0.as_ptr() }
     };
 
     quote! {
         #requests
         #events
 
-        pub static mut #interface_ident: wayland_backend::protocol::wl_interface = wayland_backend::protocol::wl_interface {
+        pub static #interface_ident: wayland_backend::protocol::wl_interface = wayland_backend::protocol::wl_interface {
             name: #name_value as *const u8 as *const std::os::raw::c_char,
             version: #version_value,
             request_count: #request_count_value,
@@ -89,15 +87,15 @@ fn gen_messages(interface: &Interface, messages: &[Message], which: &str) -> Tok
             let array_values = msg.args.iter().map(|arg| match (arg.typ, &arg.interface) {
                 (Type::Object, &Some(ref inter)) | (Type::NewId, &Some(ref inter)) => {
                     let interface_ident =format_ident!("{}_interface", inter);
-                    quote! { unsafe { &#interface_ident as *const wayland_backend::protocol::wl_interface } }
+                    quote! { &#interface_ident as *const wayland_backend::protocol::wl_interface }
                 }
-                _ => quote! { NULLPTR as *const wayland_backend::protocol::wl_interface },
+                _ => quote! { null::<wayland_backend::protocol::wl_interface>() },
             });
 
             Some(quote! {
-                static mut #array_ident: [*const wayland_backend::protocol::wl_interface; #array_len] = [
+                static #array_ident: SyncWrapper<[*const wayland_backend::protocol::wl_interface; #array_len]> = SyncWrapper([
                     #(#array_values,)*
-                ];
+                ]);
             })
         }
     });
@@ -118,17 +116,17 @@ fn gen_messages(interface: &Interface, messages: &[Message], which: &str) -> Tok
             wayland_backend::protocol::wl_message {
                 name: #name_value as *const u8 as *const std::os::raw::c_char,
                 signature: #signature_value as *const u8 as *const std::os::raw::c_char,
-                types: unsafe { &#types_ident as *const _ },
+                types: #types_ident.0.as_ptr(),
             }
         }
     });
 
     quote! {
         #(#types_arrays)*
 
-        pub static mut #message_array_ident: [wayland_backend::protocol::wl_message; #message_array_len] = [
+        static #message_array_ident: SyncWrapper<[wayland_backend::protocol::wl_message; #message_array_len]> = SyncWrapper([
             #(#message_array_values,)*
-        ];
+        ]);
     }
 }