c2rust宏指令转化规则1 - 计算机科学

# 常量宏

C 中常量宏的四种使用方式：

以下是对应的 Rust 版本的处理方案：

	macro_rules! my_def {
	($name: ident : $ty: ty, $value: expr) => {
	#[allow(non_upper_case_globals)]
	pub const $name: $ty = $value;
	};
	($name: ident, $ty: ty) => {
	#[allow(non_camel_case_types)]
	pub type $name = *mut $ty;
	};
	}

	my_def!(MAX_SIZE: i32, 1024);
	my_def!(MY_STR: &'static str, "root/api/");
	my_def!(MYTY, i32);
	my_def!(MYNIL: bool, true);

	fn main() {
	let num = MAX_SIZE;
	println!("MAX_SIZE = {}", num);

	let mystr = MY_STR;
	let user = MY_STR.to_owned() + "jiale/";
	println!("MY_STR = {}, user = {}", mystr, user);

	let jude = MYNIL;
	if jude == true {
	println!("This is MYNIL.");
	}

	let mut x: i32 = 42;
	let p: MYTY = &mut x;
	unsafe {
	*p = 123;
	println!("x = {}", x); // 输出 x = 123
	}
	}

	/*
	输出：
	MAX_SIZE = 1024
	MY_STR = root/api/, user = root/api/jiale/
	This is MYNIL.
	x = 123
	*/

	macro_rules! function_macro {
	(
	$(#[$attr:meta])*
	$vis:vis fn $name:ident ( $( $arg:ident : $t:ty ),* ) -> $ret:ty {
	$($body:tt)*
	}
	) => {
	$(#[$attr])*
	$vis fn $name ( $( $arg : $t ),* ) -> $ret {
	$($body)*
	}
	};
	}
	function_macro!(
	pub fn add(a: i32, b: i32) -> i32 {
	a + b
	}
	);
	function_macro!(
	pub fn myprint(a: i32, b: i32) -> i32 {
	println!("{}", a*b);
	a*b
	}
	);
	function_macro!(
	pub fn mymax(a: i32, b: i32) -> i32 {
	if a > b {
	a
	} else {
	b
	}
	}
	);
	function_macro!(
	pub fn mytotal(a: i32, b: i32) -> i32 {
	let mut sum = 0;
	for i in a..=b {
	sum += i;
	}
	sum
	}
	);
	function_macro! {
	pub fn factorial(n: u64) -> u64 {
	if n <= 1 {
	1
	} else {
	n * factorial(n - 1)
	}
	}
	}

	fn main() {
	let a = 1;
	let b = 2;
	let c = add(a, b);
	println!("{}", c);

	let d = myprint(a,b);
	println!("a * b = {}", d);

	let maxnum = mymax(1,2);
	println!("maxnum = {}", maxnum);

	let total = mytotal(1,10);
	println!("total = {}", total);

	let result = factorial(5);
	println!("5! = {}", result);
	}

	/*
	输出：
	3
	2
	a * b = 2
	maxnum = 2
	total = 55
	5! = 120
	*/