是否可以在编译时从环境变量初始化变量? [英] Is it possible to initialize a variable from an environment variable at compilation time?

问题描述

我想在编译期间初始化一个变量.比如我想在编译代码时将变量VAR初始化为VALUE:

I would like to initialize a variable during compilation time. For example, I would like to initialize the variable VAR to VALUE when compiling the code:

match env::var("VAR") {
    Ok(value) => println!("Ok {}", value),
    Err(e) => println!("Error ({})", e),
};

但是，我想在 no_std 上下文中执行此操作，因此，我无法使用 std::env 访问环境.可以这样做吗?

However, I wanted to do it in a no_std context, therefore, I cannot use std::env to access the environment. Is it possible to do this?

推荐答案

env::var 在编译时不会得到评估:

从当前进程中获取环境变量键.

Fetches the environment variable key from the current process.

您正在寻找 std::env!/core::env! 或 std::option_env!/core::option_env!.

You are looking for std::env! / core::env! or std::option_env! / core::option_env!.

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