Question

这是一个最小的例子：

lib.rs：

#![feature(lang_items)]
#![no_std]

extern crate rlibc;
extern crate libc;

use libc::{c_int, c_char};

#[no_mangle] // just for easier llvm-ir reading
fn foo(baz: &str) -> usize {
    baz.len()
}

#[no_mangle]
pub extern fn main(_argc: c_int, _argv: *const *const c_char) -> c_int {
    let gdb_wait = true; // for debugging with gdb
    while unsafe { core::ptr::read_volatile(&gdb_wait) } {}

    assert_eq!(foo(&"bar_fail"), 0);
    assert_eq!(foo("bar_ok"), 6);

    loop {}
}

// just some functions to run on bare metal.

#[lang = "panic_fmt"]
#[no_mangle]
pub extern fn rust_begin_panic(_msg: core::fmt::Arguments, _file: &'static str, _line: u32) -> ! {
    loop {}
}

#[lang = "eh_personality"]
pub extern fn eh_personality() { loop {} }

#[allow(non_snake_case)]
#[no_mangle]
pub extern "C" fn _Unwind_Resume() -> ! { loop {} }

#[no_mangle]
pub extern fn fmod(_: f64, _: f64) {
    loop {  }
}

#[no_mangle]
pub extern fn fmodf(_: f32, _: f32) {
    loop {  }
}

主要功能由asm在qemu-system-x86_64上以64bit-longmode调用。

传递&&str时第一次调用的GDB输出。这不起作用：

(gdb) print baz
$1 = {data_ptr = 0x0, length = 0}

传递&str时第二次调用的GDB输出。这很好用：

(gdb) print baz
$2 = {data_ptr = 0xffffffff80133460 <str4498> "bar_oksrc/lib.rsassertion failed: `(left == right)` (left: ``, right: ``)\001gdb_load_rust_pretty_printers.py", length = 6}

这是a full runnable project。

Answer 1

通过编辑链接描述文件解决了这个问题。字符串放在内存中的bss部分之后。所以multiboot用零填充它。

从＆amp;＆amp; str强制转换为＆amp; str的值在裸机上具有空值

1 个答案: