Rust编译AArch64架构PIE库及跨Crate使用问题解决

环境信息 #

• 系统：Ubuntu 20.04 x86_64
• Rust版本：rustc 1.69.0-nightly
• 目标平台：aarch64-unknown-none-softfloat（已安装对应rust-std组件）

问题重现与分析 #

1. PIE库（libtest）编译问题 #

libtest的src/lib.rs代码：

#![feature(restricted_std)]                        

pub fn add(left: usize, right: usize) -> usize {
    left + right
}

pub fn output(i: usize) {
    println!("i:{}", i);
}

Cargo.toml配置：

[package]                                                               
name = "libtest"
version = "0.1.0"
edition = "2021"

[dependencies]

[lib]
crate-type = ["lib"]
version = "0.1.0"

最初编译错误

执行命令：

cargo build --lib --target=aarch64-unknown-none-softfloat -Clink-args="-pie"

报错：

warning: unused manifest key: lib.version
Compiling libtest v0.1.0 (/home/user/libtest)
error[E0463]: can't find crate for std
|
= note: the aarch64-unknown-none-softfloat target may not support the standard library
= note: std is required by libtest because it does not declare #![no_std]
= help: consider building the standard library from source with cargo build -Zbuild-std

error: cannot find macro println in this scope
--> src/lib.rs:8:5
|
8 | println!("i:{}", i);
| ^^^^^^^

error[E0635]: unknown feature restricted_std
--> src/lib.rs:1:12
|
1 | #![feature(restricted_std)]
| ^^^^^^^^^^^^^^

错误原因：

• lib.version是无效字段，Cargo的[lib]段不支持version配置
• aarch64-unknown-none-softfloat属于无标准库目标，默认没有std，需通过-Zbuild-std编译std
• restricted_std特性在1.69.0-nightly中不存在，无需启用

修正后编译成功

执行命令：

cargo rustc --target aarch64-unknown-none-softfloat --release -Zbuild-std -- -Clink-args="-pie"

生成文件：libtest/target/aarch64-unknown-none-softfloat/release/liblibtest.rlib

2. 在pie_test项目中使用libtest的问题 #

pie_test的src/main.rs代码：

extern crate libtest;                                                                                                   
fn main() {
    println!("Hello, world!");
    let a = libtest::add(1, 2); 
    println!("finish test {}", a); 
}

Cargo.toml配置：

[package]                                                                                                               
name = "pie_test"
version = "0.1.0"
edition = "2021"

[dependencies]
libtest = { path = "./liblibtest.rlib" }

目录结构：

├── Cargo.lock
├── Cargo.toml
├── liblibtest.rlib
├── rust-toolchain.toml
└── src
    └── main.rs

编译错误1（rustc命令）

执行命令：

rustc src/main.rs --target aarch64-unknown-none-softfloat --extern libtest=./liblibtest.rlib

报错：

error[E0463]: can't find crate for std
|
= note: the aarch64-unknown-none-softfloat target may not support the standard library
= note: std is required by <unknown> because it does not declare #![no_std]
= help: consider building the standard library from source with cargo build -Zbuild-std

error[E0463]: can't find crate for std which libtest depends on
--> src/main.rs:1:1
|

extern crate libtest;
^^^^^^^^^^^^^^^^^^^^^ can't find crate

= note: the aarch64-unknown-none-softfloat target may not support the standard library
= help: consider building the standard library from source with cargo build -Zbuild-std

error: cannot find macro println in this scope
--> src/main.rs:5:5
|
5 | println!("finish test {}", a);
| ^^^^^^^

error: cannot find macro println in this scope
--> src/main.rs:3:5
|
3 | println!("Hello, world!");
| ^^^^^^^

error: #[panic_handler] function required, but not found

error: aborting due to 5 previous errors

错误原因：目标平台无默认std，rustc本身不支持-Zbuild-std，需通过Cargo调用编译std

编译错误2（cargo build命令）

执行命令：

cargo build --target aarch64-unknown-none-softfloat

报错：

error: failed to get libtest as a dependency of package pie_test v0.1.0 (/home/user/pie_test)

Caused by:
failed to load source for dependency libtest

Caused by:
Unable to update /home/user/pie_test/liblibtest.rlib

Caused by:
failed to read /home/user/pie_test/liblibtest.rlib/Cargo.toml

Caused by:
Not a directory (os error 20)

错误原因：Cargo的path依赖需指向包含Cargo.toml的源码目录，而非编译后的.rlib文件

正确解决方案 #

步骤1：修正libtest库的配置 #

修改libtest/Cargo.toml，移除[lib]段中的无效version字段：

[package]                                                               
name = "libtest"
version = "0.1.0"
edition = "2021"

[dependencies]

[lib]
crate-type = ["lib"]

移除src/lib.rs中的无效特性声明：

pub fn add(left: usize, right: usize) -> usize {
    left + right
}

pub fn output(i: usize) {
    println!("i:{}", i);
}

步骤2：重新编译libtest库 #

执行命令：

cd libtest
cargo rustc --target aarch64-unknown-none-softfloat --release -Zbuild-std -- -Clink-args="-pie"

步骤3：正确配置pie_test项目依赖 #

修改pie_test/Cargo.toml，将libtest的依赖指向其源码目录（假设libtest与pie_test同级）：

[package]                                                                                                               
name = "pie_test"
version = "0.1.0"
edition = "2021"

[dependencies]
libtest = { path = "../libtest" }

步骤4：编译pie_test项目 #

执行命令：

cd pie_test
cargo build --target aarch64-unknown-none-softfloat --release -Zbuild-std

可选：直接使用已编译的.rlib文件 #

若必须使用预编译的.rlib，需通过Cargo间接调用rustc并指定std依赖：

cd pie_test
cargo rustc --target aarch64-unknown-none-softfloat --release -Zbuild-std --extern libtest=./liblibtest.rlib -- -Clink-args="-pie"

内容的提问来源于stack exchange，提问作者si yan