在zig中使用opencv，错误：lld-link：未定义符号：cv :: imread

Question

我正在尝试在zig编程语言中使用opencv，我尝试按照我在stackoverflow post上读到的内容在zig语言中使用opencv c ++库，我创建了一个opencv_binding.h文件，其中包含一个简单的函数称为 doSomething 只调用 imread 函数

opencv_binding.h：

void doSomething(void);

opencv_binding.cpp：

#include <opencv2/core/core.hpp>
#include <opencv2/imgcodecs/imgcodecs.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>

extern "C" void doSomething(void) {
    cv::Mat image = cv::imread("sample.png", cv::IMREAD_COLOR);

}

build.zig：

const std = @import("std");

// Although this function looks imperative, note that its job is to
// declaratively construct a build graph that will be executed by an external
// runner.
pub fn build(b: *std.Build) void {
    // Standard target options allows the person running `zig build` to choose
    // what target to build for. Here we do not override the defaults, which
    // means any target is allowed, and the default is native. Other options
    // for restricting supported target set are available.
    const target = b.standardTargetOptions(.{});

    // Standard optimization options allow the person running `zig build` to select
    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
    // set a preferred release mode, allowing the user to decide how to optimize.
    const optimize = b.standardOptimizeOption(.{});

    const exe = b.addExecutable(.{
        .name = "opencv_test",
        // In this case the main source file is merely a path, however, in more
        // complicated build scripts, this could be a generated file.
        .root_source_file = .{ .path = "src/main.zig" },
        .target = target,
        .optimize = optimize,
    });

    exe.linkLibC();
    exe.linkLibCpp();
    
    exe.addIncludePath("C:/OpenCV/build/include");
    exe.addLibraryPath("C:/OpenCV/build/x64/vc16/lib");
    exe.linkSystemLibrary("opencv_world470");
    
    exe.addIncludePath("src");
    exe.addCSourceFile("src/opencv_binding.cpp", &.{});

    // This declares intent for the executable to be installed into the
    // standard location when the user invokes the "install" step (the default
    // step when running `zig build`).
    b.installArtifact(exe);

    // This *creates* a Run step in the build graph, to be executed when another
    // step is evaluated that depends on it. The next line below will establish
    // such a dependency.
    const run_cmd = b.addRunArtifact(exe);

    // By making the run step depend on the install step, it will be run from the
    // installation directory rather than directly from within the cache directory.
    // This is not necessary, however, if the application depends on other installed
    // files, this ensures they will be present and in the expected location.
    run_cmd.step.dependOn(b.getInstallStep());

    // This allows the user to pass arguments to the application in the build
    // command itself, like this: `zig build run -- arg1 arg2 etc`
    if (b.args) |args| {
        run_cmd.addArgs(args);
    }

    // This creates a build step. It will be visible in the `zig build --help` menu,
    // and can be selected like this: `zig build run`
    // This will evaluate the `run` step rather than the default, which is "install".
    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);

    // Creates a step for unit testing. This only builds the test executable
    // but does not run it.
    const unit_tests = b.addTest(.{
        .root_source_file = .{ .path = "src/main.zig" },
        .target = target,
        .optimize = optimize,
    });

    const run_unit_tests = b.addRunArtifact(unit_tests);

    // Similar to creating the run step earlier, this exposes a `test` step to
    // the `zig build --help` menu, providing a way for the user to request
    // running the unit tests.
    const test_step = b.step("test", "Run unit tests");
    test_step.dependOn(&run_unit_tests.step);
}

注意：这些是我添加到

build.zig

文件中的行：

    exe.linkLibC();
    exe.linkLibCpp();
    
    exe.addIncludePath("C:/OpenCV/build/include");
    exe.addLibraryPath("C:/OpenCV/build/x64/vc16/lib");
    exe.linkSystemLibrary("opencv_world470");
    
    exe.addIncludePath("src");
    exe.addCSourceFile("src/opencv_binding.cpp", &.{});

在 build.zig 文件中，我链接了 opencv_world.lib 库，但是在编译时出现一些错误：

error: lld-link: undefined symbol: cv::imread(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&, int)
error: lld-link: undefined symbol: cv::Mat::~Mat()

我该如何解决这个问题？

Answer 1

我最近在 Linux 上构建的 opencv v4.8.0 和 zig 0.11 也遇到了同样的问题。您的问题可能是使用没有 stdc++ 链接编译的 opencv。

您可以尝试在 build.zig 中添加 stc++ 库

exe.linkSystemLibrary("stdc++");

请注意，zig 0.11 现在是默认值，本地路径链接略有不同：

exe.addIncludePath(.{ .path = "src" });

或者，也许更好，从包含 stdc++ 的源代码构建 opencv。我用 Zig 成功构建了。

CC="zig cc" CXX="zig c++" cmake \
-D CMAKE_BUILD_TYPE=RELEASE \
-D WITH_IPP=OFF \
-D WITH_OPENGL=OFF \
-D WITH_QT=OFF \
-D CMAKE_INSTALL_PREFIX=/usr/local \
-D OPENCV_EXTRA_MODULES_PATH=../../opencv_contrib/modules/ \
-D OPENCV_ENABLE_NONFREE=ON \
-D WITH_JASPER=OFF \
-D WITH_TBB=ON \
-D BUILD_DOCS=OFF \
-D BUILD_EXAMPLES=OFF \
-D BUILD_TESTS=OFF \
-D BUILD_PERF_TESTS=OFF \
-D BUILD_opencv_java=NO \
-D BUILD_opencv_python=NO \
-D BUILD_opencv_python2=NO \
-D BUILD_opencv_python3=NO \
-D OPENCV_GENERATE_PKGCONFIG=ON \
..

make -j8
make preinstall
sudo make install
sudo ldconfig