ChunMinChang

mod sys;

use std::ffi::CString;
use std::os::raw::c_void;
use std::{thread, time::Duration};

// A macro to print the function name
macro_rules! function {
    () => {{
        fn f() {}

ChunMinChang

all:
				# Build a static library from the Rust file
				rustc --crate-type=staticlib ext.rs
				# Compile the C file with the static library
				# gcc -o sample-c sample.c libext.a
				gcc -o sample sample.c -L. -lext
				./sample
clean:
				rm libext.a
				rm sample

ChunMinChang

// A module containing all the types and APIs in the external library.
mod sys {
    use std::cmp;
    use std::ffi::CString;
    use std::os::raw::{c_char, c_void};

    pub type XString = *mut c_void;

    extern "C" {
        fn calloc(items: usize, size: usize) -> *mut c_void;

ChunMinChang

all:
				# Sample in C(static library):
				# gcc -c string_ref.c -o string_ref.o
				# ar rcs libstringref.a string_ref.o
				# gcc -c device.c -o device.o
				# ar rcs libdevice.a device.o
				# gcc sample.c -L. -ldevice -lstringref -o sample-c
				# ./sample-c

				# Sample in C:

ChunMinChang

all:
				# Build a static library from the Rust file
				rustc --crate-type=staticlib ext.rs
				# Compile the C file with the static library
				# gcc -o sample-c sample.c libext.a
				gcc -o sample-c sample.c -L. -lext
				./sample-c
				# g++ -o sample-cpp sample.cpp libext.a
				g++ -o sample-cpp sample.cpp -L. -lext
				./sample-cpp

ChunMinChang

Don't misuse the pointers of the instances allocated in functions stack

struct Foo { ... }

fn create_foo() -> Foo {
    let foo = Foo { ... };
    foo
}

ChunMinChang

A counterexample to register the callback functions to the external libraries

The key point for this gist repo is to indicate:

Don't misuse the pointers of the instances allocated in functions stack since they will be gone after finishing the function calling.

The sample code here is to demonstrate the problem I have when I am developing a [Rust audio library][draft]. To play sounds, it needs to register callbacks to the underlying OS through audio APIs and then the callbacks will be fired periodically. The callback usually will come with at least 2 parameters:

1. a buffer that will be filled with audio data
2. a pointer indicating what variable calls the callback.

To create Rust APIs that can play audio, I create a struct for audio stream named Stream and store all the stream related settings like sampling rate or channels in that struct. There is a struct method named new that will create a Stream instance that will be returnd. Before the instance is returned, I use the pointer of

ChunMinChang

#[path = ""]
mod utils {
    #[path = "audio_object.rs"]
    mod audio_object;

    use self::audio_object::{get_property_data, sys::*};
    use std::fmt; // For fmt::{Display, Formatter, Formatter}

    #[derive(PartialEq)]
    pub enum Scope {

ChunMinChang

all:
				# Sample in C:
				# gcc -shared -fPIC device.c -o libdevice.so
				# gcc sample.c libdevice.so -o sample-c
				# ./sample-c

				# Sample in C++:
				g++ -std=c++11 -shared -fPIC device.cpp -o libdevice.so
				g++ -std=c++11 sample.cpp libdevice.so -o sample-cpp
				./sample-cpp

ChunMinChang

#include <cassert>

typedef int NewType;

struct A {
  NewType a;
};

struct B {
  NewType b;