rust处理全局变量的策略

Rust 的静态变量不会在程序退出时自动调用 Drop，因为它们的生命周期与进程绑定。

use std::sync::OnceLock;

struct GlobalData {
    content: String,
}

impl Drop for GlobalData {
    fn drop(&mut self) {
        println!("Cleaning up: {}", self.content);
    }
}

static GLOBAL_DATA: OnceLock<GlobalData> = OnceLock::new();

fn main() {
    GLOBAL_DATA.get_or_init(|| GlobalData {
        content: "Hello, world!".to_string(),
    });

    println!("Program is running...");
    // When the program exits, the Drop implementation for GlobalData is called.
}

Program is running...

方法1：在main中自动Drop全局变量

全局变量的生命周期应该和main的程序生命周期是一样长的，所以可以在main中创建一个CleanUp局部对象，为CleanUp()实现Drop特征，在Drop()特征中，完成释放全局变量的资源的功能。

struct Cleanup;

impl Drop for Cleanup {
    fn drop(&mut self) {
	    //调用某些全局变量的释放方法 或者 C库中的方法
        println!("Cleanup executed on program exit.");
    }
}

fn main() {
    let _cleanup = Cleanup; // The `Drop` method will be called when `_cleanup` goes out of scope
    
    println!("Program is running...");
}

测试：

Program is running...
Cleanup executed on program exit.

eg:

use std::sync::OnceLock;

struct Cleanup;


impl Drop for Cleanup {
    fn drop(&mut self) {
    GlobalData::free();
        println!("Cleanup executed on program exit.");
    }
}

struct GlobalData {
    content: String,
}


impl GlobalData{
    
    pub fn free()
    {
        println!("GlobalData::free...");
    }
    
}


static GLOBAL_DATA: OnceLock<GlobalData> = OnceLock::new();

fn main() {

    GLOBAL_DATA.get_or_init(|| GlobalData {
        content: "Hello, world!".to_string(),
    });

    let _cleanup = Cleanup; // The `Drop` method will be called when `_cleanup` goes out of scope
    
    println!("Program is running...");
}

Program is running...
GlobalData::free...
Cleanup executed on program exit.

参考