如何在conanfile.py安装阶段修改Conan包解决UE4与OpenCV冲突

问题背景 #

我们的项目基于Unreal Engine 4.26.2和OpenCV 3.4.0（需保留该旧版本），正在将原有OpenCV构建Shell脚本转换为Conan配方。构建最终应用时，遇到OpenCV与UE4的int64和uint64定义冲突的问题。

原有Shell脚本通过修补OpenCV安装目录下的头文件解决该冲突，具体补丁内容如下：

--- opencv2/core/hal/interface.old.h    2019-11-26 12:34:40.260333132 +0300
+++ opencv2/core/hal/interface.h    2019-11-26 17:13:27.232585976 +0300
@@ -58,8 +58,8 @@
 #  define CV_BIG_INT(n)   n##I64
 #  define CV_BIG_UINT(n)  n##UI64
 #else
-   typedef int64_t int64;
-   typedef uint64_t uint64;
+//   typedef int64_t int64;
+//   typedef uint64_t uint64;
 #  define CV_BIG_INT(n)   n##LL
 #  define CV_BIG_UINT(n)  n##ULL
 #endif

原有Shell脚本核心逻辑 #

原有脚本先克隆代码、编译安装OpenCV，最后对安装目录的头文件打补丁：

git clone --depth=1 https://github.com/opencv/opencv.git -b 3.4.0
git clone --depth=1 https://github.com/opencv/opencv_contrib.git -b 3.4.0

mkdir build
cd build
cmake .. .....
make 
make install

patch -N -p4 $INSTALL_DIR/include/opencv2/core/hal/interface.h $SCRIPT_DIR/opencv_02.patch

现有Conan配方及修改方案 #

现有Conan配方已实现克隆、编译安装逻辑，需在cmake.install()后添加补丁操作，对安装目录的头文件进行修改。

修改后的完整Conan配方代码 #

from conans import ConanFile, CMake, tools
import os

class OpenCVUE4Conan(ConanFile):
    name = "opencv-ue4"
    version = "3.4.0"
    url = ""
    description = "OpenCV custom build for UE4"
    license = "BSD"
    settings = "os", "compiler", "build_type", "arch"
    generators = "cmake"
    # 新增冲突修复补丁到导出列表
    exports_sources = 'patches/cmakes.patch', 'patches/check_function.patch', 'patches/opencv_02.patch'
    
    def requirements(self):
        self.requires("ue4util/ue4@adamrehn/profile")
        self.requires("zlib/ue4@adamrehn/{}".format(self.channel))
        self.requires("UElibPNG/ue4@adamrehn/{}".format(self.channel))

    def cmake_flags(self):
        flags = [
            "-DOPENCV_ENABLE_NONFREE=OFF",
            # 其他编译参数
        ]
        return flags

    def source(self):
        self.run("git clone --depth=1 https://github.com/opencv/opencv.git -b {}".format(self.version))
        self.run("git clone --depth=1 https://github.com/opencv/opencv_contrib.git -b {}".format(self.version))

    def build(self):
        # 应用编译前的补丁，跳过冲突修复补丁
        for p in self.exports_sources:
            if p.endswith(".patch") and not p.endswith("opencv_02.patch"):
                tools.patch(base_path='opencv', patch_file=p, fuzz=True)

        cmake = CMake(self)
        cmake.configure(source_folder="opencv", args=self.cmake_flags())
        cmake.build()
        cmake.install()
        
        # 对安装目录的头文件应用冲突修复补丁
        install_include_dir = os.path.join(self.package_folder, "include")
        target_header = os.path.join(install_include_dir, "opencv2", "core", "hal", "interface.h")
        tools.patch(file_path=target_header, patch_file="patches/opencv_02.patch", fuzz=True)

修改说明 #

1. 新增补丁文件导出：将opencv_02.patch添加到exports_sources列表，确保Conan能读取到该补丁文件。
2. 区分补丁时机：编译前只应用原有两个补丁，避免提前修改源码影响编译流程；安装完成后再对安装目录的头文件打冲突修复补丁，和原有Shell脚本逻辑完全对齐。
3. 定位目标文件：通过self.package_folder获取Conan的安装目录，精准定位到需要修改的interface.h头文件，执行补丁操作。

内容的提问来源于stack exchange，提问作者wl2776