Add no_std support in objc_exception

Author: madsmtm

objc_exception/Cargo.toml

@@ -6,6 +6,7 @@ edition = "2018"
 
 description = "Rust interface for Objective-C's throw and try/catch statements."
 keywords = ["objective-c", "osx", "ios"]
+categories = ["development-tools::ffi", "no-std"]
 repository = "http://github.com/SSheldon/rust-objc-exception"
 documentation = "http://ssheldon.github.io/rust-objc/objc_exception/"
 license = "MIT"

objc_exception/extern/exception.m

@@ -2,7 +2,8 @@
 // See https://clang.llvm.org/docs/AutomaticReferenceCounting.html#arc-runtime-objc-retain
 id objc_retain(id value);
 
-int RustObjCExceptionTryCatch(void (*try)(void *), void *context, id *error) {
+// We return `unsigned char`, since it is guaranteed to be an `u8` on all platforms
+unsigned char RustObjCExceptionTryCatch(void (*try)(void *), void *context, id *error) {
     @try {
         try(context);
         if (error) {

objc_exception/src/lib.rs

@@ -1,8 +1,13 @@
 //! Rust interface for Objective-C's `@throw` and `@try`/`@catch` statements.
 
-use std::mem;
-use std::os::raw::{c_int, c_void};
-use std::ptr;
+#![no_std]
+
+#[cfg(test)]
+extern crate alloc;
+
+use core::ffi::c_void;
+use core::mem;
+use core::ptr;
 
 #[link(name = "objc", kind = "dylib")]
 // TODO: "C-unwind"
@@ -20,7 +25,7 @@ extern "C" {
         r#try: extern "C" fn(*mut c_void),
         context: *mut c_void,
         error: *mut *mut c_void,
-    ) -> c_int;
+    ) -> u8; // std::os::raw::c_uchar
 }
 
 /// An opaque type representing any Objective-C object thrown as an exception.
@@ -100,8 +105,10 @@ where
 
 #[cfg(test)]
 mod tests {
+    use alloc::string::ToString;
+    use core::ptr;
+
     use super::{r#try, throw};
-    use std::ptr;
 
     #[test]
     fn test_try() {