Question

我试图在我的Rust项目中包含一个C文件。 C文件使用系统依赖性。以下是运行cargo build时无法编译的最小示例。

如果我收到执行Cargo的失败命令，并附加了"-l" "nl-genl-3" "-l" "nl-3"，则命令成功成功。是否将链接器标志放在错误的位置，因为这些标志在命令中肯定是？

src / main.rs

#[link(name = "nl-genl-3")]
#[link(name = "nl-3")]
extern "C" {
    fn nl_test(help_me_pls: usize) -> usize;
}

fn main() {
    unsafe {
        println!("nl.c function result: {:?}", nl_test(6));
    }
}

src / nl.c

#include <linux/nl80211.h>
#include <netlink/netlink.h>
#include <netlink/genl/genl.h>

int nl_test(int help_me_pls) {
    struct nl_sock* socket = nl_socket_alloc();
    nl_socket_free(socket);
    return help_me_pls;
}

build.rs

extern crate cc;

fn main() {
    cc::Build::new()
        .include("/usr/include/libnl3")
        .file("src/nl.c")
        .compile("libnl.a");
}

Cargo.toml

[package]
name = "derp"
version = "0.1.0"

[build-dependencies]
cc = "1.0"

运行cargo build

时得到以下输出

   Compiling cc v1.0.18
   Compiling derp v0.1.0 (file:///root/derp)
error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-L" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib" "/root/derp/target/debug/deps/derp-5a7445c256565e2d.1vmrdj4gsxr690x4.rcgu.o" "/root/derp/target/debug/deps/derp-5a7445c256565e2d.1y16o1qfye96o7m0.rcgu.o" "/root/derp/target/debug/deps/derp-5a7445c256565e2d.3rngp6bm2u2q5z0y.rcgu.o" "/root/derp/target/debug/deps/derp-5a7445c256565e2d.4oc10dk278mpk1vy.rcgu.o" "/root/derp/target/debug/deps/derp-5a7445c256565e2d.4xq48u46a1pwiqn7.rcgu.o" "/root/derp/target/debug/deps/derp-5a7445c256565e2d.51s1w397y42gpez1.rcgu.o" "/root/derp/target/debug/deps/derp-5a7445c256565e2d.8xzrsc1ux72v29j.rcgu.o" "/root/derp/target/debug/deps/derp-5a7445c256565e2d.oa3rad818d8sgn4.rcgu.o" "-o" "/root/derp/target/debug/deps/derp-5a7445c256565e2d" "/root/derp/target/debug/deps/derp-5a7445c256565e2d.crate.allocator.rcgu.o" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-nodefaultlibs" "-L" "/root/derp/target/debug/deps" "-L" "/root/derp/target/debug/build/derp-c3cdcf1fbd0c70b2/out" "-L" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib" "-l" "nl-genl-3" "-l" "nl-3" "-Wl,-Bstatic" "-Wl,--whole-archive" "-l" "nl" "-Wl,--no-whole-archive" "-Wl,--start-group" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/libstd-774f1a5992f88ec5.rlib" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/libpanic_unwind-a65ab1ab71045d14.rlib" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/liballoc_jemalloc-5cced33d7a39db8e.rlib" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/libunwind-76fba694360269fc.rlib" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/liballoc_system-b3f660c2be971c37.rlib" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/liblibc-64d840c62d40ace0.rlib" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/liballoc-b3d8b67c899d207d.rlib" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/libcore-d9124265921c5963.rlib" "-Wl,--end-group" "/root/.rustup/toolchains/stable-armv7-unknown-linux-gnueabihf/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/libcompiler_builtins-1aad7d9a81def783.rlib" "-Wl,-Bdynamic" "-l" "dl" "-l" "rt" "-l" "pthread" "-l" "pthread" "-l" "gcc_s" "-l" "c" "-l" "m" "-l" "rt" "-l" "pthread" "-l" "util" "-l" "util"
  = note: /root/derp/target/debug/build/derp-c3cdcf1fbd0c70b2/out/libnl.a(nl.o): In function `nl_test':
          /root/derp/src/nl.c:6: undefined reference to `nl_socket_alloc'
          /root/derp/src/nl.c:7: undefined reference to `nl_socket_free'
          collect2: error: ld returned 1 exit status

Answer 1

来自Cargo documentation for build scripts：

rustc-link-lib=[KIND=]NAME表示指定的值是库名称，应作为-l标志传递给编译器。的可选的KIND可以是static，dylib（默认）或framework中的一个，有关更多详细信息，请参见rustc --help。

将此添加到您的构建脚本中：

println!("cargo:rustc-link-lib=nl-genl-3");
println!("cargo:rustc-link-lib=nl-3");

并从Rust代码中删除link属性。

问题是您的链接器标志声明Rust代码需要链接到C库，但这不是完全正确的。您的 C代码需要链接到库，而Rust代码需要链接到已编译的C代码。如果您查看自变量，您将看到此（精简的）输出

deps/derp-5a7445c256565e2d.1vmrdj4gsxr690x4.rcgu.o（您的Rust代码）
-l nl-genl-3（系统库）
-l nl-3（系统库）
-l nl（您的C垫片）

链接器的参数顺序很重要。如果链接器处理对象时不需要某些内容，则将不使用。

在这里，Rust代码在nl库中添加了对代码的依赖关系，因此链接器正在寻找这些符号。处理nl-3和nl-genl-3时，我们不需要它们中的任何符号，因此大多数情况下会忽略它们。在处理nl时，我们从Rust代码解决了相关性，但是nl需要nl-genl-3和nl-3中的符号，将不再对其进行处理。

这不是很明显，但是compile中的cc方法会自动打印出一条cargo:rustc-link-lib行，以将其构建结果绑定到您的Rust代码中。

另请参阅：

Answer 2

这就是我解决它的方法Rust + .so lib。希望有帮助

如何将库链接到我的C代码并在Rust二进制文件中使用它？

2 个答案: