如何在Windows x64机器上用64位rustc链接x86 .lib库？

问题 #

我在x64架构的Windows机器上构建Rust应用，需要链接一个暴露C接口的x86架构C++静态库ClientAuth.lib。已通过64位rustup-init.exe安装Rust，执行cargo build时出现以下链接错误：

= note: sanitized_auth_test_1.qvct9jv5vjn41op.rcgu.o : error LNK2019: unresolved external symbol encryptLogonAuth referenced in function _ZN21sanitized_auth_test_14main17hf80bd6c03de31c54E
          sanitized_auth_test_1.qvct9jv5vjn41op.rcgu.o : error LNK2019: unresolved external symbol initEncryption referenced in function _ZN21sanitized_auth_test_14main17hf80bd6c03de31c54E
          lib\\ClientAuth.lib : warning LNK4272: library machine type 'x86' conflicts with target machine type 'x64'
          C:\Users\XXX\development\sanitized_auth_test_1\target\debug\deps\sanitized_auth_test_1.exe : fatal error LNK1120: 2 unresolved externals

已尝试在VS 2022的x64原生工具命令提示符、x86_64交叉工具命令提示符以及x86原生工具命令提示符中执行编译，但错误一致。

环境信息 #

• Rust版本：

rustc 1.70.0-nightly (700938c07 2023-04-04)
binary: rustc
commit-hash: 700938c0781c9f135244bb1ec846fe1a5e03ae7d
commit-date: 2023-04-04
host: x86_64-pc-windows-msvc
release: 1.70.0-nightly
LLVM version: 16.0.0

• Cargo版本：

cargo 1.70.0-nightly (0e474cfd7 2023-03-31)
release: 1.70.0-nightly
commit-hash: 0e474cfd7b16b018cf46e95da3f6a5b2f1f6a9e7
commit-date: 2023-03-31
host: x86_64-pc-windows-msvc
libgit2: 1.5.0 (sys:0.16.0 vendored)
libcurl: 8.0.1-DEV (sys:0.4.61+curl-8.0.1 vendored ssl:Schannel)
os: Windows 10.0.22000 (Windows 10 Pro) [64-bit]

项目结构 #

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----          4/6/2023   8:00 AM                include
d-----          4/6/2023   8:00 AM                lib
d-----          4/6/2023   7:56 AM                src
d-----          4/6/2023   8:01 AM                target
-a----          4/5/2023  12:09 PM              9 .gitignore
-a----          4/6/2023   7:58 AM            228 build.rs
-a----          4/6/2023   7:58 AM            165 Cargo.lock
-a----          4/6/2023   7:58 AM            178 Cargo.toml

关键文件内容 #

1. include/ClientAuth.h：

#pragma once

#ifdef __cplusplus
extern "C"
{
#endif          /* __cplusplus */
        void initEncryption(void);
        int encryptLogonAuth(   unsigned int sessionID,
                                                        unsigned int vendorID,
                                                        unsigned int productID,
                                                        unsigned int bigEndian,
                                                        char* outBuff);
#ifdef __cplusplus
}
#endif          /* __cplusplus */

2. src/main.rs：

use std::os::raw::c_char;
#[link(name = "ClientAuth", kind = "static")]
extern "C" {
    fn initEncryption();
    fn encryptLogonAuth(
        session_id: u32,
        vendor_id: u32,
        product_id: u32,
        big_endian: u32,
        out_buff: *mut c_char,
    ) -> i32;
}

fn main() {
    let session_id: u32 = 0;
    let vendor_id: u32 = 0;
    let big_endian: u32 = 0;
    let product_id: u32 = 0;
    let mut out_buff: [c_char; 16] = Default::default();

    unsafe {
        let _ = encryptLogonAuth(
            session_id,
            vendor_id,
            product_id,
            big_endian,
            out_buff.as_mut_ptr(),
        );
        initEncryption();
    }
}

3. build.rs：

fn main() {
    println!("cargo:rustc-link-search=lib/");
    println!("cargo:rustc-link-lib=ClientAuth");
    println!("cargo:rerun-if-changed=src/main.rs");
    println!("cargo:rerun-if-changed=include/ClientAuth.h");
}

4. Cargo.toml：

[package]
name = "sanitized_auth_test_1"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

由于无法获取库的源码重新编译，请问是否有办法在x64机器上使用64位cargo/rustc链接x86架构的ClientAuth.lib库？

解答 #

核心结论 #

无法直接用64位Rust工具链链接x86架构的静态库，x64与x86属于不同指令集架构，链接器无法匹配跨架构的符号，这是底层架构限制，没有绕过的办法。

可行解决方案：切换Rust到x86目标编译 #

既然无法重新编译库，只能将Rust程序编译为32位（x86），与库的架构匹配。步骤如下：

1. 安装x86目标的Rust工具链
   打开命令提示符执行：

rustup target add i686-pc-windows-msvc

2. 指定x86目标编译程序
   在VS 2022的x86原生工具命令提示符中执行：

cargo build --target i686-pc-windows-msvc

3. 验证编译结果
   编译完成后，32位程序会生成在target/i686-pc-windows-msvc/debug目录下，可直接在x64 Windows系统上通过WoW64兼容层运行。

为什么之前尝试x86命令提示符无效？ #

之前的操作未指定--target i686-pc-windows-msvc参数，Rust默认使用x64目标编译，即使在x86工具环境中，依然会生成64位程序，导致架构不匹配的错误。

内容的提问来源于stack exchange，提问作者Matthew Pittenger