Add initial sys crate for blocks, improving GNUStep support

Author: madsmtm

.github/workflows/gnustep.yml

@@ -101,18 +101,17 @@ jobs:
       uses: actions-rs/cargo@v1
       with:
         command: check
-        args: --verbose --no-default-features
+        args: --verbose --no-default-features --features gnustep-1-9
 
-    - name: Test GNUStep
+    - name: Test without features
       uses: actions-rs/cargo@v1
       with:
         command: test
-        # Temporary fix
-        args: --verbose --no-fail-fast --no-default-features --package objc2_sys --package objc2 --package objc2_encode --package objc2_exception --package objc2_foundation
+        args: --verbose --no-fail-fast --no-default-features --features gnustep-1-9
 
-    - name: Test GNUStep with features
+    - name: Test with features
       uses: actions-rs/cargo@v1
       with:
         command: test
-        # Temporary fix
-        args: --verbose --no-fail-fast --no-default-features --features exception,verify_message --package objc2_sys --package objc2 --package objc2_encode --package objc2_exception --package objc2_foundation
+        # Not using --all-features because some features are nightly-only
+        args: --verbose --no-fail-fast --features gnustep-1-9,block,exception,verify_message

Cargo.toml

@@ -2,6 +2,7 @@
 members = [
     "objc2",
     "objc2_block",
+    "objc2_block_sys",
     "objc2_encode",
     "objc2_exception",
     "objc2_foundation",

objc2_block/Cargo.toml

@@ -23,6 +23,7 @@ exclude = [
 
 [dependencies]
 objc2_encode = { path = "../objc2_encode" }
+objc2_block_sys = { path = "../objc2_block_sys" }
 
 [dev-dependencies]
 objc2_test_utils = { path = "../objc2_test_utils" }

objc2_block/src/lib.rs

@@ -63,26 +63,9 @@ use core::ops::{Deref, DerefMut};
 use core::ptr;
 use std::os::raw::{c_int, c_ulong};
 
+pub use objc2_block_sys as ffi;
 use objc2_encode::{Encode, EncodeArguments, Encoding, RefEncode};
 
-// TODO: Replace with `objc2::Class`
-#[repr(C)]
-struct ClassInternal {
-    _priv: [u8; 0],
-}
-
-#[cfg_attr(target_vendor = "apple", link(name = "System", kind = "dylib"))]
-#[cfg_attr(
-    not(target_vendor = "apple"),
-    link(name = "BlocksRuntime", kind = "dylib")
-)]
-extern "C" {
-    static _NSConcreteStackBlock: ClassInternal;
-
-    fn _Block_copy(block: *const c_void) -> *mut c_void;
-    fn _Block_release(block: *const c_void);
-}
-
 /// Types that may be used as the arguments to an Objective-C block.
 pub trait BlockArguments: Sized {
     /// Calls the given `Block` with self as the arguments.
@@ -151,7 +134,7 @@ block_args_impl!(
 
 #[repr(C)]
 struct BlockBase<A, R> {
-    isa: *const ClassInternal,
+    isa: *const ffi::Class,
     flags: c_int,
     _reserved: c_int,
     invoke: unsafe extern "C" fn(*mut Block<A, R>, ...) -> R,
@@ -207,7 +190,7 @@ impl<A, R> RcBlock<A, R> {
     ///
     /// The given pointer must point to a valid `Block`.
     pub unsafe fn copy(ptr: *mut Block<A, R>) -> Self {
-        let ptr = _Block_copy(ptr as *const c_void) as *mut Block<A, R>;
+        let ptr = ffi::_Block_copy(ptr as *const c_void) as *mut Block<A, R>;
         RcBlock { ptr }
     }
 }
@@ -229,7 +212,7 @@ impl<A, R> Deref for RcBlock<A, R> {
 impl<A, R> Drop for RcBlock<A, R> {
     fn drop(&mut self) {
         unsafe {
-            _Block_release(self.ptr as *const c_void);
+            ffi::_Block_release(self.ptr as *const c_void);
         }
     }
 }
@@ -397,7 +380,7 @@ impl<A, R, F> ConcreteBlock<A, R, F> {
     unsafe fn with_invoke(invoke: unsafe extern "C" fn(*mut Self, ...) -> R, closure: F) -> Self {
         ConcreteBlock {
             base: BlockBase {
-                isa: &_NSConcreteStackBlock,
+                isa: &ffi::_NSConcreteStackBlock,
                 // 1 << 25 = BLOCK_HAS_COPY_DISPOSE
                 flags: 1 << 25,
                 _reserved: 0,

objc2_block_sys/Cargo.toml

@@ -0,0 +1,53 @@
+[package]
+name = "objc2_block_sys"
+version = "0.0.0" # Remember to update html_root_url in lib.rs
+authors = ["Mads Marquart <mads@marquart.dk>"]
+edition = "2018"
+
+description = "Raw bindings to Apple's C language extension of blocks"
+keywords = ["objective-c", "macos", "ios", "blocks", "sys"]
+categories = [
+    "external-ffi-bindings",
+    # "no_std", # TODO
+    "os::macos-apis",
+]
+repository = "https://github.com/madsmtm/objc2"
+documentation = "https://docs.rs/objc2_block_sys/"
+license = "MIT"
+
+# readme = "README.md"
+
+# Downstream users can customize the linking!
+# See https://doc.rust-lang.org/cargo/reference/build-scripts.html#overriding-build-scripts
+links = "block"
+build = "build.rs"
+
+[features]
+# Link to Apple's libclosure (exists in libSystem)
+# See https://opensource.apple.com/source/libclosure/
+# Accessible mirror https://github.com/madsmtm/libclosure
+#
+# This is the default on Apple platforms
+apple = []
+
+# Link to libBlocksRuntime from compiler-rt
+# See https://github.com/llvm/llvm-project/tree/release/13.x/compiler-rt/lib/BlocksRuntime
+#
+# This is the default on non-Apple platforms
+compiler-rt = []
+
+# Link to GNUStep's libobjc2 (which contains the block implementation)
+gnustep-1-7 = ["objc2_sys"]
+gnustep-1-8 = ["gnustep-1-7"]
+gnustep-1-9 = ["gnustep-1-8"]
+gnustep-2-0 = ["gnustep-1-9"]
+gnustep-2-1 = ["gnustep-2-0"]
+
+# Link to Microsoft's libobjc2
+winobjc = ["gnustep-1-8"]
+
+# TODO
+objfw = []
+
+[dependencies]
+objc2_sys = { path = "../objc2_sys", optional = true }

objc2_block_sys/build.rs

@@ -0,0 +1,63 @@
+use std::env;
+use std::path::Path;
+
+fn main() {
+    // Only rerun if this file changes; the script doesn't depend on our code
+    println!("cargo:rerun-if-changed=build.rs");
+
+    let mut apple = env::var_os("CARGO_FEATURE_APPLE").is_some();
+    let mut compiler_rt = env::var_os("CARGO_FEATURE_COMPILER_RT").is_some();
+    let gnustep = env::var_os("CARGO_FEATURE_GNUSTEP_1_7").is_some();
+    let objfw = env::var_os("CARGO_FEATURE_OBJFW").is_some();
+
+    if let (false, false, false, false) = (apple, compiler_rt, gnustep, objfw) {
+        let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
+        if let "macos" | "ios" | "tvos" | "watchos" = &*target_os {
+            apple = true;
+            // Add cheaty #[cfg(feature = "apple")] directive
+            println!("cargo:rustc-cfg=feature=\"apple\"");
+        } else {
+            compiler_rt = true;
+            // Add cheaty #[cfg(feature = "compiler-rt")] directive
+            println!("cargo:rustc-cfg=feature=\"compiler-rt\"");
+        }
+    }
+
+    let mut cc_args = "-fblocks".to_owned();
+
+    match (apple, compiler_rt, gnustep, objfw) {
+        (true, false, false, false) => {
+            // Link to libclosure (internally called libsystem_blocks), which is
+            // exported by libSystem.dylib.
+            //
+            // Note that System.framework is just a deprecated wrapper over the
+            // dynamic library.
+            println!("cargo:rustc-link-lib=dylib=System");
+            // Alternative: Only link to libsystem_blocks.dylib
+            // println!("cargo:rustc-link-search=native=/usr/lib/system");
+            // println!("cargo:rustc-link-lib=dylib=system_blocks");
+        }
+        (false, true, false, false) => {
+            println!("cargo:rustc-link-lib=dylib=BlocksRuntime");
+        }
+        (false, false, true, false) => {
+            // Don't link to anything; objc2_sys already does that for us!
+
+            // Add GNUStep compability headers to make `#include <Block.h>`
+            // work (on newer GNUStep versions these headers are present)
+            if !env::var_os("CARGO_FEATURE_GNUSTEP_2_0").is_some() {
+                let compat_headers =
+                    Path::new(env!("CARGO_MANIFEST_DIR")).join("gnustep-compat-headers");
+                cc_args.push_str("-I");
+                cc_args.push_str(compat_headers.to_str().unwrap());
+            }
+        }
+        (false, false, false, true) => unimplemented!(),
+        // Checked in if-let above
+        (false, false, false, false) => unreachable!(),
+        (_, _, _, _) => panic!("Invalid feature combination; only one runtime may be selected!"),
+    }
+
+    // Add DEP_BLOCK_CC_ARGS
+    println!("cargo:cc_args={}", cc_args);
+}

objc2_block_sys/gnustep-compat-headers/Block.h

@@ -0,0 +1 @@
+#include <objc/blocks_runtime.h>

objc2_block_sys/gnustep-compat-headers/Block_private.h

@@ -0,0 +1 @@
+#include <objc/blocks_private.h>

objc2_block_sys/src/lib.rs

@@ -0,0 +1,39 @@
+//!
+//! See:
+//! - https://github.com/apple/swift-corelibs-libdispatch/tree/main/src/BlocksRuntime
+//! - https://clang.llvm.org/docs/BlockLanguageSpec.html
+//! - https://clang.llvm.org/docs/Block-ABI-Apple.html
+
+// Update in Cargo.toml as well.
+#![doc(html_root_url = "https://docs.rs/objc2_block_sys/0.0.0")]
+
+use core::ffi::c_void;
+
+#[repr(C)]
+pub struct Class {
+    #[cfg(any(feature = "apple", feature = "compiler-rt"))]
+    _priv: [*mut c_void; 32],
+    #[cfg(any(feature = "gnustep-1-7", feature = "objfw"))]
+    // The size of this is unknown
+    _priv: [u8; 0],
+}
+
+extern "C" {
+    // the raw data space for runtime classes for blocks
+    // class+meta used for stack, malloc, and collectable based blocks
+
+    pub static _NSConcreteGlobalBlock: Class;
+    pub static _NSConcreteStackBlock: Class;
+    pub static _NSConcreteMallocBlock: Class;
+
+    pub fn _Block_copy(block: *const c_void) -> *mut c_void;
+    pub fn _Block_release(block: *const c_void);
+
+    /// Runtime entry point called by compiler when assigning objects inside
+    /// copy helper routines
+    pub fn _Block_object_assign(dest_addr: *mut c_void, object: *const c_void, flags: i32);
+
+    /// runtime entry point called by the compiler when disposing of objects
+    /// inside dispose helper routine
+    pub fn _Block_object_dispose(object: *const c_void, flags: i32);
+}

objc2_test_utils/Cargo.toml

@@ -18,5 +18,8 @@ license = "MIT"
 
 build = "build.rs"
 
+[dependencies]
+objc2_block_sys = { path = "../objc2_block_sys" }
+
 [build-dependencies]
 cc = "1.0"