Building lib with a c++ dependency usind cmake-rs

help
1

Hi, i have created a simple lib using cxx that used a external c++ lib as a dependency, i was able to compile and link this lib using cmake-rs, but for some reason when i tried to use the lib i get a error from the compiler saying it was unable to find the c++ lib a have used as a dependency.

The build.rs file of the lib:

use cmake::Config;

fn main() {
    cxx_build::bridge("src/lib.rs")
        .file("cpp/main.cpp")
        .flag_if_supported("-std=c++17")
        .compile("cxx-bridge");

    let dst = Config::new("cpp")
        .cxxflag("-std=c++17")
        .env("REALM_CPP_NO_TESTS", "ON")
        .env("CMAKE_CXX_FLAGS", "-fpermissive -Wchanges-meaning")
        .build();

    println!("cargo:rustc-link-search=native={}", dst.display());
    println!("cargo:rustc-link-lib=cpprealm");

    println!("cargo:rerun-if-changed=src/lib.rs");
    println!("cargo:rerun-if-changed=cpp/main.cpp");
    println!("cargo:rerun-if-changed=cpp/main.h");
}

When runing cargo build on the lib itself it compiles without any problem, but when i try to run it as a dependency of another project i receive the error:

  = note: /usr/bin/ld: cannot find -lcpprealm: No such file or directory
          collect2: error: ld returned 1 exit status

I don't have many experience using cpp code with rust so any help is much appreciated.

2

Your search path is probably wrong. Make sure path in dst exists and contains libcpprealm.a (unix) or cpprealm.lib (on windows)

3

exactly. when it is build as standalone crate, the output directory "happens to" be picked up by the linker.

the Config::build() returns the path to the library, but the linker search path expects a list of directories that contains the library. I think Path::parent() should do the trick.

    println!("cargo:rustc-link-search=native={}", dst.parent().unwrap().display());
4

I verified the target output and discovered that the lib was located on the a sub-directory of the path received by dst.display().

replacing

println!("cargo:rustc-link-search=native={}", dst.parent().unwrap().display());

with

println!("cargo:rustc-link-search=native={}/build", dst.display());

solved my problem. Thanks everyone for the help.

5

What is realm_rs?

6

The name of the lib I was compiling

7

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