Update readme

README.md

@@ -1,7 +1,7 @@
 # CPAL - Cross-Platform Audio Library
 
 [![Actions Status](https://github.com/RustAudio/cpal/workflows/cpal/badge.svg)](https://github.com/RustAudio/cpal/actions)
- [![Crates.io](https://img.shields.io/crates/v/cpal.svg)](https://crates.io/crates/cpal) [![docs.rs](https://docs.rs/cpal/badge.svg)](https://docs.rs/cpal/)
+[![Crates.io](https://img.shields.io/crates/v/cpal.svg)](https://crates.io/crates/cpal) [![docs.rs](https://docs.rs/cpal/badge.svg)](https://docs.rs/cpal/)
 
 Low-level library for audio input and output in pure Rust.
 
@@ -51,19 +51,20 @@ WASAPI including access to large numbers of channels and lower-latency audio
 processing.
 
 CPAL allows for using the ASIO SDK as the audio host on Windows instead of
-WASAPI. 
+WASAPI.
 
 ### Locating the ASIO SDK
 
 The location of ASIO SDK is exposed to CPAL by setting the `CPAL_ASIO_DIR` environment variable.
 
-The build script will try to find the ASIO SDK by following these steps in order:  
+The build script will try to find the ASIO SDK by following these steps in order:
+
 1. Check if `CPAL_ASIO_DIR` is set and if so use the path to point to the SDK.
 2. Check if the ASIO SDK is already installed in the temporary directory, if so use that and set the path of `CPAL_ASIO_DIR` to the output of `std::env::temp_dir().join("asio_sdk")`.
 3. If the ASIO SDK is not already installed, download it from <https://www.steinberg.net/asiosdk> and install it in the temporary directory. The path of `CPAL_ASIO_DIR` will be set to the output of `std::env::temp_dir().join("asio_sdk")`.
 
 In an ideal situation you don't need to worry about this step.
- 
+
 ### Preparing the build environment
 
 1. `bindgen`, the library used to generate bindings to the C++ SDK, requires
@@ -80,28 +81,33 @@ In an ideal situation you don't need to worry about this step.
    and install ASIO4ALL**](http://www.asio4all.org/). Be sure to enable the
    "offline" feature during installation despite what the installer says about
    it being useless.
-4. Our build script assumes that Microsoft Visual Studio is installed. The script will try to find `vcvarsall.bat` 
-   and execute it with the right machine architecture regardless of the Microsoft Visual Studio version. 
-   If there are any errors encountered in this process which is unlikely, 
-   you may find the `vcvarsall.bat` manually and execute it with your machine architecture as an argument. 
+4. Our build script assumes that Microsoft Visual Studio is installed if the host OS for compilation is Windows. The script will try to find `vcvarsall.bat`
+   and execute it with the right host and target machine architecture regardless of the Microsoft Visual Studio version.
+   If there are any errors encountered in this process which is unlikely,
+   you may find the `vcvarsall.bat` manually and execute it with your machine architecture as an argument.
    The script will detect this and skip the step.
-   
+
    A manually executed command example for 64 bit machines:
+
    ```
    "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvarsall.bat" amd64
    ```
+
+   For more information please refer to the documentation of [`vcvarsall.bat``](https://docs.microsoft.com/en-us/cpp/build/building-on-the-command-line?view=msvc-160#vcvarsall-syntax).
+
 5. Select the ASIO host at the start of our program with the following code:
 
    ```rust
    let host;
    #[cfg(target_os = "windows")]
    {
-       host = cpal::host_from_id(cpal::HostId::Asio).expect("failed to initialise ASIO host");
+      host = cpal::host_from_id(cpal::HostId::Asio).expect("failed to initialise ASIO host");
    }
    ```
 
    If you run into compilations errors produced by `asio-sys` or `bindgen`, make
    sure that `CPAL_ASIO_DIR` is set correctly and try `cargo clean`.
+
 6. Make sure to enable the `asio` feature when building CPAL:
 
    ```
@@ -114,5 +120,23 @@ In an ideal situation you don't need to worry about this step.
    ```toml
    cpal = { version = "*", features = ["asio"] }
    ```
-
-*Updated as of ASIO version 2.3.3.*
+
+_Updated as of ASIO version 2.3.3._
+
+### Cross compilation
+
+When Windows is the host and the target OS, the build script of `asio-sys` supports all cross compilation targets
+which are supported by the MSVC compiler. An exhaustive list of combinations could be found [here](https://docs.microsoft.com/en-us/cpp/build/building-on-the-command-line?view=msvc-160#vcvarsall-syntax) with the addition of undocumented `arm64`, `arm64_x86`, `arm64_amd64` and `arm64_arm` targets. (5.11.2023)
+
+It is also possible to compile Windows applications with ASIO support on Linux and macOS.
+
+For both platforms the common way to do this is to use the [MinGW-w64](https://www.mingw-w64.org/) toolchain.
+
+Make sure that you have included the `MinGW-w64` include directory in your `CPLUS_INCLUDE_PATH` environment variable.
+Make sure that LLVM is installed and include directory is also included in your `CPLUS_INCLUDE_PATH` environment variable.
+
+Example for macOS for the target of `x86_64-pc-windows-gnu` where `mingw-w64` is installed via brew:
+
+```
+export CPLUS_INCLUDE_PATH="$CPLUS_INCLUDE_PATH:/opt/homebrew/Cellar/mingw-w64/11.0.1/toolchain-x86_64/x86_64-w64-mingw32/include"
+```

asio-sys/Cargo.toml

@@ -17,7 +17,7 @@ parse_cfg = "4.1.1"
 
 [dependencies]
 once_cell = "1.12"
-num-derive = "0.4"
+num-derive = "0.3"
 num-traits = "0.2"