我如何将库链接到我的C代码并在一个锈蚀二进制文件中使用它？

Question

我试图在我的锈菌项目中包括一个C文件。C文件使用系统依赖项。下面是一个在运行cargo build时不编译的最小示例。

如果我接受货运正在运行的失败命令，并附加了"-l" "nl-genl-3" "-l" "nl-3"，则该命令确实成功。它是不是把链接器标志放错了地方，因为这些标志肯定在命令中？

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"

当我运行cargo build时，我得到以下输出

   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

来自构建脚本的货运文档

rustc-link-lib=[KIND=]NAME表示指定的值是一个库名，应该作为-l标志传递给编译器。可选的KIND可以是static、dylib (默认值)或framework中的一个，有关详细信息，请参阅rustc --help。

将此添加到构建脚本中：

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

并从锈蚀代码中删除link属性。

问题是您的链接器标志正在声明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，而您的Rust代码需要链接到编译的C代码。如果您查看参数，您将看到以下(简写)输出

• deps/derp-5a7445c256565e2d.1vmrdj4gsxr690x4.rcgu.o (您的锈蚀代码)
• -l nl-genl-3 (系统库)
• -l nl-3 (系统库)
• -l nl (你的C垫片)

链接者的论点顺序很重要。如果在链接器处理对象时不需要某些东西，则不会使用它。

在这里，锈蚀代码添加了一个依赖于来自nl库的代码，因此链接器正在监视这些符号。当nl-3和nl-genl-3被处理时，我们不需要它们的任何符号，所以它们大多被忽略。当nl被处理时，我们解析了锈蚀代码中的依赖项，但是nl需要来自nl-genl-3和nl-3的符号，这些符号将不再被处理。

这并不明显，但是来自cc的cc方法会自动打印出一条cargo:rustc-link-lib行，以便将其构建结果与您的Rust代码相关联。

另请参阅：

• 如何在Rust中指定链接器路径？
• 将Rust应用程序链接到运行时链接器搜索路径之外的动态库

Answer 2

这就是我是如何解决它的铁锈+ .so库。希望能帮上忙