objc_direct methods are emitted as msg_send! instead of a direct C call

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
objective-c, rust
Domain
tooling

Research direction

Start in ir/objc.rs at the CXCursor_ObjCInstanceMethodDecl handling and reproduce the issue with the bindgen invocation shown in the report. Trace how objc_direct attributes are exposed by libclang and how the generated method call is selected. Done means objc_direct methods generate a direct C FFI declaration with the expected link name rather than an objc::msg_send! wrapper.

Written by the indexing model from the issue text.

Description

Input C/C++ Header
__attribute__((objc_root_class))
@interface Foo {
    Class isa;
}
- (int)bar:(int)x __attribute__((objc_direct));
@end
Bindgen Invocation
$ bindgen input.h -- -x objective-c -fobjc-arc
Actual Results

bindgen 0.72.1 and 0.73.1 both emit an objc::msg_send! wrapper:

unsafe fn bar_(&self, x: c_int) -> c_int {
    msg_send!(*self, bar: x)
}

Clang compiles an objc_direct method as an ordinary C function, not as a messenger entry:

define hidden i32 @"\01-[Foo bar:]"(ptr noundef %0, i32 noundef %1)

nm shows a defined symbol -[Foo bar:]. Direct methods are not added to the class's method list, so objc_msgSend cannot find bar:.

ir/objc.rs walks CXCursor_ObjCInstanceMethodDecl and always builds a msg_send! call. There is no check for ObjCDirectAttr / objc_direct.

Expected Results

Emit a direct C FFI declaration for objc_direct methods (extern "C" { #[link_name = "\u{1}-[Foo bar:]"] fn ... }), not msg_send!.

Environment
bindgen: 0.72.1 and 0.73.1 (rust-lang/rust-bindgen 77cbc723)
clang/libclang: Apple clang 21.0.0
rustc: 1.97.1
target: aarch64-apple-darwin
OS: macOS
Dominant language
Rust
Stars
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Forks
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Avg merge
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Merged PRs (30d)
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