如何在Rust FFI中访问C全局变量/常量? [英] How can I access a C global variable/constant in Rust FFI?

问题描述

我需要访问Rust中从C导出的常量值.

I need to access a value of a constant exported from C in Rust.

我想从实际符号中读取值，而不仅仅是将值复制并粘贴到Rust(在我的情况下，该值是一个指针，而C检查指针是否相等).

I want to read the value from the actual symbol, and not just copy'n'paste the value to Rust (in my case the value is a pointer, and C checks for pointer equality).

extern void *magic;

要使魔术:* const c_void 在Rust中可读的语法是什么?

What's the syntax to get magic: *const c_void readable in Rust?

推荐答案

use std::os::raw::c_void;

extern "C" {
    #[no_mangle]
    static magic: *const c_void;
}

可选地，在 extern 之前可以有#[link(kind ="static"，name =< c库名称"))] 获取实际链接的符号.

Optionally, before the extern there can be #[link(kind="static", name="<c library name>")] to get the symbol actually linked.

即使是常量，也可以使用 static 声明外部可链接项，而不仅仅是 const 关键字(否则，您将获得外部项不能为 const ").

Externally linkable items, even if constant, need be declared with static, not just const keyword (otherwise you get "extern items cannot be const").

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