Add static classes

Author: madsmtm

.github/workflows/ci.yml

@@ -395,12 +395,12 @@ jobs:
         # Not using --all-features because that would enable e.g. gnustep
         args: ${{ env.ARGS }} ${{ env.TESTARGS }} --features ${{ env.FEATURES }},${{ env.UNSTABLE_FEATURES }}
 
-    - name: Test static selectors
+    - name: Test static class and selectors
       if: ${{ !matrix.dinghy && (matrix.runtime || 'apple') == 'apple' }}
       uses: actions-rs/cargo@v1
       with:
         command: test
-        args: ${{ env.ARGS }} ${{ env.TESTARGS }} --features unstable-static-sel
+        args: ${{ env.ARGS }} ${{ env.TESTARGS }} --features unstable-static-sel,unstable-static-class
 
     - name: Run assembly tests
       if: ${{ !contains(matrix.runtime, 'compiler-rt') }}

objc2-foundation/src/declare_macro.rs

@@ -515,7 +515,7 @@ macro_rules! declare_class {
                 use $crate::__std::sync::Once;
 
                 use $crate::objc2::declare::ClassBuilder;
-                use $crate::objc2::runtime::Protocol;
+                use $crate::objc2::runtime::{Class, Protocol};
                 static REGISTER_CLASS: Once = Once::new();
 
                 REGISTER_CLASS.call_once(|| {
@@ -555,7 +555,8 @@ macro_rules! declare_class {
                     let _cls = builder.register();
                 });
 
-                $crate::objc2::class!($name)
+                // We just registered the class, so it should be available
+                Class::get(stringify!($name)).unwrap()
             }
         }
 

objc2/CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## Unreleased - YYYY-MM-DD
 
+### Added
+* Added the `"unstable-static-class"` and `"unstable-static-class-inlined"`
+  feature flags to make the `class!` macro zero cost.
+
 
 ## 0.3.0-beta.1 - 2022-07-19
 

objc2/Cargo.toml

@@ -51,6 +51,8 @@ malloc = ["malloc_buf"]
 # https://github.com/madsmtm/objc2/issues/new
 unstable-static-sel = ["objc2-proc-macros"]
 unstable-static-sel-inlined = ["unstable-static-sel"]
+unstable-static-class = ["objc2-proc-macros"]
+unstable-static-class-inlined = ["unstable-static-class"]
 
 # Uses nightly features to make AutoreleasePool zero-cost even in debug mode
 unstable-autoreleasesafe = []

objc2/examples/introspection.rs

@@ -4,6 +4,10 @@ use objc2::{class, msg_send, msg_send_id};
 #[cfg(feature = "malloc")]
 use objc2::{sel, Encode};
 
+#[cfg(feature = "apple")]
+#[link(name = "Foundation", kind = "framework")]
+extern "C" {}
+
 fn main() {
     // Get a class
     let cls = class!(NSObject);

objc2/examples/talk_to_me.rs

@@ -12,6 +12,9 @@ use std::ffi::c_void;
 #[cfg(feature = "apple")]
 #[link(name = "AVFoundation", kind = "framework")]
 extern "C" {}
+#[cfg(feature = "apple")]
+#[link(name = "Foundation", kind = "framework")]
+extern "C" {}
 
 const UTF8_ENCODING: NSUInteger = 4;
 

objc2/src/lib.rs

@@ -218,6 +218,11 @@ mod test_utils;
 #[cfg(feature = "malloc")]
 mod verify;
 
+// Hack to make doctests work
+#[cfg(all(feature = "apple", feature = "unstable-static-class"))]
+#[link(name = "Foundation", kind = "framework")]
+extern "C" {}
+
 /// Hacky way to make GNUStep link properly to Foundation while testing.
 ///
 /// This is a temporary solution to make our CI work for now!

objc2/src/macros.rs

@@ -1,14 +1,35 @@
 /// Gets a reference to a [`Class`] from the given name.
 ///
+/// [`Class`]: crate::runtime::Class
+///
+///
 /// # Panics
 ///
 /// Panics if no class with the given name can be found.
 ///
 /// To check for a class that may not exist, use [`Class::get`].
 ///
-/// [`Class`]: crate::runtime::Class
 /// [`Class::get`]: crate::runtime::Class::get
 ///
+///
+/// # Features
+///
+/// If the experimental `"unstable-static-class"` feature is enabled, this
+/// will emit special statics that will be replaced by dyld when the program
+/// starts up.
+///
+/// Errors that were previously runtime panics may now turn into linker errors
+/// if you try to use a class which is not available. Additionally, you may
+/// have to call `msg_send![cls, class]` on the result if you want to use it
+/// in a dynamic context (e.g. dynamically declaring classes).
+///
+/// See the [corresponding section][sel#features] in the [`sel!`] macro for
+/// more details on the limitations of this. The
+/// `"unstable-static-class-inlined"` corresponds to the
+/// `"unstable-static-sel-inlined"` feature here.
+///
+/// [sel#features]: crate::sel#features
+///
 /// # Examples
 ///
 /// ```no_run
@@ -17,6 +38,15 @@
 /// ```
 #[macro_export]
 macro_rules! class {
+    ($name:ident) => {{
+        $crate::__class_inner!($name)
+    }};
+}
+
+#[doc(hidden)]
+#[macro_export]
+#[cfg(not(feature = "unstable-static-class"))]
+macro_rules! __class_inner {
     ($name:ident) => {{
         use $crate::__macro_helpers::{concat, panic, stringify, CachedClass, None, Some};
         static CACHED_CLASS: CachedClass = CachedClass::new();
@@ -177,18 +207,12 @@ macro_rules! __sel_inner {
 
 #[doc(hidden)]
 #[macro_export]
-macro_rules! __sel_inner_statics_apple_generic {
+macro_rules! __inner_statics_apple_generic {
     {
+        @image_info;
         $image_info_section:literal;
-        $var_name_section:literal;
-        $selector_ref_section:literal;
-        $data:expr,
         $($idents:ident)+
     } => {
-        use $crate::__macro_helpers::{u8, UnsafeCell};
-        use $crate::ffi::__ImageInfo;
-        use $crate::runtime::Sel;
-
         /// We always emit the image info tag, since we need it to:
         /// - End up in the same codegen unit as the other statics below.
         /// - End up in the final binary so it can be read by dyld.
@@ -202,7 +226,17 @@ macro_rules! __sel_inner_statics_apple_generic {
             $crate::__macro_helpers::__hash_idents!($($idents)+),
         )]
         #[used] // Make sure this reaches the linker
-        static _IMAGE_INFO: __ImageInfo = __ImageInfo::system();
+        static _IMAGE_INFO: $crate::ffi::__ImageInfo = $crate::ffi::__ImageInfo::system();
+    };
+    {
+        @sel;
+        $var_name_section:literal;
+        $selector_ref_section:literal;
+        $data:expr,
+        $($idents:ident)+
+    } => {
+        use $crate::__macro_helpers::{u8, UnsafeCell};
+        use $crate::runtime::Sel;
 
         const X: &[u8] = $data.as_bytes();
 
@@ -262,47 +296,128 @@ macro_rules! __sel_inner_statics_apple_generic {
             UnsafeCell::new(Sel::__internal_from_ptr(NAME_DATA.as_ptr().cast()))
         };
     };
+    {
+        @class;
+        $class_ref_section:literal;
+        $name:ident
+    } => {
+        use $crate::__macro_helpers::UnsafeCell;
+        use $crate::runtime::Class;
+
+        extern "C" {
+            /// Link to the Objective-C class static.
+            ///
+            /// This uses the special symbol that static and dynamic linkers
+            /// knows about.
+            ///
+            /// Failure modes:
+            /// - Unknown class: Static linker error.
+            /// - OS version < Class introduced version: Dynamic linker error
+            ///   on program startup.
+            /// - Deployment target > Class introduced version: No error,
+            ///   though _should_ be a static linker error.
+            ///
+            /// Ideally, we'd have some way of allowing this to be weakly
+            /// linked, and return `Option<&Class>` in that case, but Rust
+            /// doesn't have the capability to do so yet!
+            /// <https://github.com/rust-lang/rust/issues/29603>
+            /// <https://stackoverflow.com/a/16936512>
+            /// <http://sealiesoftware.com/blog/archive/2010/4/8/Do-it-yourself_Objective-C_weak_import.html>
+            #[link_name = $crate::__macro_helpers::concat!(
+                "OBJC_CLASS_$_",
+                $crate::__macro_helpers::stringify!($name),
+            )]
+            static CLASS: Class;
+        }
+
+        /// SAFETY: Same as `REF` above.
+        #[link_section = $class_ref_section]
+        #[export_name = $crate::__macro_helpers::concat!(
+            "\x01L_OBJC_CLASSLIST_REFERENCES_$_",
+            $crate::__macro_helpers::__hash_idents!($name),
+        )]
+        static mut REF: UnsafeCell<&Class> = unsafe {
+            UnsafeCell::new(&CLASS)
+        };
+    };
 }
 
+// These sections are found by reading clang/LLVM sources
 #[doc(hidden)]
 #[macro_export]
 #[cfg(all(feature = "apple", not(all(target_os = "macos", target_arch = "x86"))))]
-macro_rules! __sel_inner_statics {
-    ($($args:tt)*) => {
-        // Found by reading clang/LLVM sources
-        $crate::__sel_inner_statics_apple_generic! {
+macro_rules! __inner_statics {
+    (@image_info $($args:tt)*) => {
+        $crate::__inner_statics_apple_generic! {
+            @image_info;
             "__DATA,__objc_imageinfo,regular,no_dead_strip";
+            $($args)*
+        }
+    };
+    (@sel $($args:tt)*) => {
+        $crate::__inner_statics_apple_generic! {
+            @sel;
             "__TEXT,__objc_methname,cstring_literals";
             "__DATA,__objc_selrefs,literal_pointers,no_dead_strip";
             $($args)*
         }
     };
+    (@class $($args:tt)*) => {
+        $crate::__inner_statics_apple_generic! {
+            @class;
+            "__DATA,__objc_classrefs,regular,no_dead_strip";
+            $($args)*
+        }
+    };
 }
 
 #[doc(hidden)]
 #[macro_export]
 #[cfg(all(feature = "apple", target_os = "macos", target_arch = "x86"))]
-macro_rules! __sel_inner_statics {
-    ($($args:tt)*) => {
-        $crate::__sel_inner_statics_apple_generic! {
+macro_rules! __inner_statics {
+    (@image_info $($args:tt)*) => {
+        $crate::__inner_statics_apple_generic! {
+            @image_info;
             "__OBJC,__image_info,regular";
+            $($args)*
+        }
+    };
+    (@sel $($args:tt)*) => {
+        $crate::__inner_statics_apple_generic! {
+            @sel;
             "__TEXT,__cstring,cstring_literals";
             "__OBJC,__message_refs,literal_pointers,no_dead_strip";
             $($args)*
         }
     };
+    (@class $($args:tt)*) => {
+        // TODO
+        $crate::__macro_helpers::compile_error!(
+            "The `\"unstable-static-class\"` feature is not yet supported on 32bit macOS!"
+        )
+        // TODO: module info
+    };
 }
 
 #[doc(hidden)]
 #[macro_export]
 #[cfg(not(feature = "apple"))]
-macro_rules! __sel_inner_statics {
-    ($($args:tt)*) => {
+macro_rules! __inner_statics {
+    (@image_info $($args:tt)*) => {
+        // TODO
+    };
+    (@sel $($args:tt)*) => {
         // TODO
         $crate::__macro_helpers::compile_error!(
             "The `\"unstable-static-sel\"` feature is not yet supported on GNUStep!"
         )
     };
+    (@class $($args:tt)*) => {
+        // TODO
+        $crate::__macro_helpers::compile_error!(
+            "The `\"unstable-static-class\"` feature is not yet supported on GNUStep!"
+        )
+    };
 }
 
 #[doc(hidden)]
@@ -312,8 +427,9 @@ macro_rules! __sel_inner_statics {
     not(feature = "unstable-static-sel-inlined")
 ))]
 macro_rules! __sel_inner {
-    ($($args:tt)*) => {{
-        $crate::__sel_inner_statics!($($args)*);
+    ($data:expr, $($idents:ident)+) => {{
+        $crate::__inner_statics!(@image_info $($idents)+);
+        $crate::__inner_statics!(@sel $data, $($idents)+);
 
         /// HACK: Wrap the access in a non-generic, `#[inline(never)]`
         /// function to make the compiler group it into the same codegen unit
@@ -340,8 +456,44 @@ macro_rules! __sel_inner {
 #[macro_export]
 #[cfg(all(feature = "unstable-static-sel-inlined"))]
 macro_rules! __sel_inner {
-    ($($args:tt)*) => {{
-        $crate::__sel_inner_statics!($($args)*);
+    ($data:expr, $($idents:ident)+) => {{
+        $crate::__inner_statics!(@image_info $($idents)+);
+        $crate::__inner_statics!(@sel $data, $($idents)+);
+
+        #[allow(unused_unsafe)]
+        // SAFETY: See above
+        unsafe { *REF.get() }
+    }};
+}
+
+#[doc(hidden)]
+#[macro_export]
+#[cfg(all(
+    feature = "unstable-static-class",
+    not(feature = "unstable-static-class-inlined")
+))]
+macro_rules! __class_inner {
+    ($name:ident) => {{
+        $crate::__inner_statics!(@image_info $name);
+        $crate::__inner_statics!(@class $name);
+
+        #[inline(never)]
+        fn objc_static_workaround() -> &'static Class {
+            // SAFETY: Same as __sel_inner
+            unsafe { *REF.get() }
+        }
+
+        objc_static_workaround()
+    }};
+}
+
+#[doc(hidden)]
+#[macro_export]
+#[cfg(all(feature = "unstable-static-class-inlined"))]
+macro_rules! __class_inner {
+    ($name:ident) => {{
+        $crate::__inner_statics!(@image_info $name);
+        $crate::__inner_statics!(@class $name);
 
         #[allow(unused_unsafe)]
         // SAFETY: See above

objc2/src/rc/test_object.rs

@@ -130,10 +130,11 @@ impl RcTestObject {
                 builder.add_method(sel!(dealloc), dealloc as unsafe extern "C" fn(_, _));
             }
 
-            builder.register();
+            let _cls = builder.register();
         });
 
-        class!(RcTestObject)
+        // Can't use `class!` here since `RcTestObject` is dynamically created.
+        Class::get("RcTestObject").unwrap()
     }
 
     pub(crate) fn new() -> Id<Self, Owned> {