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如何将库链接到C代码并在Rust二进制文件中使用它?

ffi rust linker c

Ross MacArthur · 技术社区 · 6 年前

我正试图在我的Rust项目中包含一个C文件。C文件使用系统依赖项。下面是一个在我运行 cargo build .

如果我接受了Cargo正在运行的失败命令 "-l" "nl-genl-3" "-l" "nl-3" 命令做成功。是不是把链接器标志放错了地方,因为这些标志肯定是在指挥部?

src/主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型

#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;
}

建设资源

extern crate cc;

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

货物.toml

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

[build-dependencies]
cc = "1.0"

运行时得到以下输出 货物建造

   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

1 回复 | 直到 6 年前

Shepmaster Tim Diekmann 6 年前

从 Cargo documentation for build scripts :

rustc-link-lib=[KIND=]NAME 指示指定的值是库名称,并应作为 -l 旗帜。这个可选择的 KIND 可以是 static , dylib (违约),或 framework , 看见 rustc --help 更多细节。

将此添加到生成脚本:

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

并移除 link 从你的锈代码属性。

问题是链接器标志指出Rust代码需要链接到C库,但这并不是完全正确的。你的 C代码 需要链接到库,而Rust代码需要链接到编译的C代码。如果您查看这些参数,就会看到这个(节略的)输出

deps/derp-5a7445c256565e2d.1vmrdj4gsxr690x4.rcgu.o (你的铁锈代码)
-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什么, 不会用的 .

在这里,Rust代码添加了对 nl 库,所以链接器正在查找这些符号。什么时候? nl-3 和 nl-genl-3 是经过处理的,我们不需要它们的任何符号,所以它们大多被忽略。什么时候? 新加坡国立大学 处理后,我们从Rust代码中解析依赖关系,但是 新加坡国立大学 需要来自的符号 nl-genl-3型 和 nl-3号 ,将不再处理。

不明显,但是 compile 方法来自 cc 自动打印出 cargo:rustc-link-lib 将其生成结果绑定到锈代码中。

另见: