[question] components linking error

[JamesPei]

help! I'm using conan2 to create FFmpeg package, and this is package_info:

class ffmpegRecipe(ConanFile):
    name = "ffmpeg"
    version = "7.1"
    package_type = "application"

    url = "https://github.com/FFmpeg/FFmpeg/tree/master?tab=readme-ov-file"
    topics = ("tools", "heavy", "video", "multimedia", "codec")
    settings = "os", "arch", "compiler", "build_type"

    options = {
        "shared": [True, False],
        "with_x264": [True, False],
        "with_x265": [True, False],
        "with_GPU": [True, False],
    }
    default_options = {
        "shared": True,
        "with_x264": True,
        "with_x265": True,
        "with_GPU": False
    }

    def source(self):
        local_source_dir = os.environ.get("LOCAL_SOURCE_DIR", None)
        if local_source_dir and os.path.exists(local_source_dir):
            self.output.info(f"Using local source directory: {local_source_dir}")
            copy(self, pattern="*", src=local_source_dir, dst=self.source_folder)
        else:
            self.output.info("Cloning FFmpeg repository...")
            git = Git(self)
            git.clone(url="git@github.com:FFmpeg/FFmpeg.git", target=".")

    def config_options(self):
        if self.settings.os == "Windows":
            self.options.rm_safe("fPIC")

    def configure(self):
        if self.options.shared:
            self.options.rm_safe("fPIC")

    def build(self):
        configure_command = "./configure --prefix={} \
            --enable-gpl \
            --enable-libx264 \
            --enable-libx265".format(self.build_folder)

        if self.options.shared:
            configure_command+=" --enable-shared"

        if self.options.with_GPU:
            configure_command+=" --enable-nonfree --enable-cuda-nvcc --enable-libnpp"

        self.run(configure_command)
        self.run("make -j8")

    def package(self):
        copy(self, pattern="ffmpeg", dst=os.path.join(self.package_folder, "bin"), src=self.build_folder)
        copy(self, pattern="ffprobe", dst=os.path.join(self.package_folder, "bin"), src=self.build_folder)

        copy(self, pattern="*.h",   dst=os.path.join(self.package_folder,"include/libavcodec"),     src=os.path.join(self.build_folder,"libavcodec"))
        copy(self, pattern="*.so*", dst=os.path.join(self.package_folder,"lib"),                    src=os.path.join(self.build_folder,"libavcodec"))
        copy(self, pattern="*.h",   dst=os.path.join(self.package_folder,"include/libavdevice"),    src=os.path.join(self.build_folder,"libavdevice"))
        copy(self, pattern="*.so*", dst=os.path.join(self.package_folder,"lib"),                    src=os.path.join(self.build_folder,"libavdevice"))
        copy(self, pattern="*.h",   dst=os.path.join(self.package_folder,"include/libavfilter"),    src=os.path.join(self.build_folder,"libavfilter"))  
        copy(self, pattern="*.so*", dst=os.path.join(self.package_folder,"lib"),                    src=os.path.join(self.build_folder,"libavfilter"))
        copy(self, pattern="*.h",   dst=os.path.join(self.package_folder,"include/libavformat"),    src=os.path.join(self.build_folder,"libavformat"))  
        copy(self, pattern="*.so*", dst=os.path.join(self.package_folder,"lib"),                    src=os.path.join(self.build_folder,"libavformat"))
        copy(self, pattern="*.h",   dst=os.path.join(self.package_folder,"include/libavutil"),      src=os.path.join(self.build_folder,"libavutil"))    
        copy(self, pattern="*.so*", dst=os.path.join(self.package_folder,"lib"),                    src=os.path.join(self.build_folder,"libavutil"))
        copy(self, pattern="*.h",   dst=os.path.join(self.package_folder,"include/libpostproc"),    src=os.path.join(self.build_folder,"libpostproc"))  
        copy(self, pattern="*.so*", dst=os.path.join(self.package_folder,"lib"),                    src=os.path.join(self.build_folder,"libpostproc"))
        copy(self, pattern="*.h",   dst=os.path.join(self.package_folder,"include/libswresample"),  src=os.path.join(self.build_folder,"libswresample"))
        copy(self, pattern="*.so*", dst=os.path.join(self.package_folder,"lib"),                    src=os.path.join(self.build_folder,"libswresample"))
        copy(self, pattern="*.h",   dst=os.path.join(self.package_folder,"include/libswscale"),     src=os.path.join(self.build_folder,"libswscale"))
        copy(self, pattern="*.so*", dst=os.path.join(self.package_folder,"lib"),                    src=os.path.join(self.build_folder,"libswscale"))

    def package_info(self):
        self.cpp_info.components["avutil"].libs = ["avutil"]
        self.cpp_info.components["avutil"].set_property("cmake_target_name", "avutil")

        self.cpp_info.components["avcodec"].libs = ["avcodec"]
        self.cpp_info.components["avcodec"].requires = ["avutil"]
        self.cpp_info.components["avcodec"].set_property("cmake_target_name", "avcodec")

        self.cpp_info.components["avformat"].set_property("cmake_target_name", "avformat")
        self.cpp_info.components["avformat"].libs = ["avforamt"]
        self.cpp_info.components["avformat"].requires = ["avcodec", "avutil"]

        self.cpp_info.components["swscale"].libs = ["swscale"]
        self.cpp_info.components["swscale"].requires = ["avutil"]
        self.cpp_info.components["swscale"].set_property("cmake_target_name", "swscale")

        self.cpp_info.components["swresample"].libs = ["swresample"]
        self.cpp_info.components["swresample"].requires = ["avutil"]
        self.cpp_info.components["swresample"].set_property("cmake_target_name", "swresample")

        self.cpp_info.components["postproc"].libs = ["postproc"]
        self.cpp_info.components["postproc"].requires = ["avutil"]
        self.cpp_info.components["postproc"].set_property("cmake_target_name", "postproc")

        self.cpp_info.components["avfilter"].libs = ["avfilter"]
        self.cpp_info.components["avfilter"].requires = ["avutil", "swscale", "postproc", "avformat", "avcodec", "swresample"]
        self.cpp_info.components["avfilter"].set_property("cmake_target_name", "avfilter")

        self.cpp_info.components["avdevice"].libs = ["avdevice"]
        self.cpp_info.components["avdevice"].requires = ["avutil", "avformat", "avcodec", "avfilter"]
        self.cpp_info.components["avdevice"].set_property("cmake_target_name", "avdevice")

and then I tried to use it to build another project，here is some information:

def requirements(self):
        self.requires("ffmpeg/[~7.1]")
        self.requires("cxxopts/[~3.2]")
        self.requires("nlohmann_json/[~3.11]")

def system_requirements(self):
        Apt(self).install(["libvdpau-dev", "libx11-dev", "libva-dev"])

def build_requirements(self):
        self.tool_requires("cmake/[~3.22]")

def layout(self):
        cmake_layout(self)

def generate(self):
        deps = CMakeDeps(self)
        deps.check_components_exist = True
        deps.generate()
        tc = CMakeToolchain(self)
        tc.generate()

def build(self):
        cmake = CMake(self)
        cmake.configure()
        cmake.build()

def package(self):
        cmake = CMake(self)
        cmake.install()

it reports undefined reference to xxx' error, like undefined reference toavcodec_open2'; so I check generated cmake by CMakeDeps generator, and in ffmpeg-release-x86_64-data.cmake I found all xxx_LIBS_RELEASE is not setted, for example

set(ffmpeg_avutil_INCLUDE_DIRS_RELEASE )
set(ffmpeg_avutil_LIB_DIRS_RELEASE "${ffmpeg_PACKAGE_FOLDER_RELEASE}/lib")
set(ffmpeg_avutil_BIN_DIRS_RELEASE "${ffmpeg_PACKAGE_FOLDER_RELEASE}/bin")
set(ffmpeg_avutil_LIBRARY_TYPE_RELEASE UNKNOWN)
set(ffmpeg_avutil_IS_HOST_WINDOWS_RELEASE 0)
set(ffmpeg_avutil_RES_DIRS_RELEASE )
set(ffmpeg_avutil_DEFINITIONS_RELEASE )
set(ffmpeg_avutil_OBJECTS_RELEASE )
set(ffmpeg_avutil_COMPILE_DEFINITIONS_RELEASE )
set(ffmpeg_avutil_COMPILE_OPTIONS_C_RELEASE "")
set(ffmpeg_avutil_COMPILE_OPTIONS_CXX_RELEASE "")
set(ffmpeg_avutil_LIBS_RELEASE )
set(ffmpeg_avutil_SYSTEM_LIBS_RELEASE )
set(ffmpeg_avutil_FRAMEWORK_DIRS_RELEASE )
set(ffmpeg_avutil_FRAMEWORKS_RELEASE )
set(ffmpeg_avutil_DEPENDENCIES_RELEASE )
set(ffmpeg_avutil_SHARED_LINK_FLAGS_RELEASE )
set(ffmpeg_avutil_EXE_LINK_FLAGS_RELEASE )
set(ffmpeg_avutil_NO_SONAME_MODE_RELEASE FALSE)

so why ffmpeg_avutil_LIBS_RELEASE is not setted? Did I miss some configuration item? If I manually add a value, it works

[memsharded]

Hi @JamesPei

Some quick preliminary feedback:

• First, why aren't you using the ffmpeg recipe from ConanCenter? You can pick it from the conan-center-index repo.
• The package_type = "application" seems incorrect. You shouldn't have this type for something that is a library, and the package_info is defining all the library information. Better use package_type = "library", even if it contains one executable, the main use case is a library.
• git.clone(url="git@github.com:FFmpeg/FFmpeg.git", target=".") this is broken. A Conan recipe shouldn't be just fetching code at head, without a specific tag or commit. See the comments and warnings in https://docs.conan.io/2/tutorial/creating_packages/handle_sources_in_packages.html
• For the package() method, I'd encourage to use a for loop that iterates over the libs to do the copy(). That way is more difficult to have typos or mistakes that would skip copying some library.

I will be trying the package_type change, it can be the reason.

[memsharded]

I confirm, changing package_type = "library" works.

[JamesPei]

@memsharded thank you sir, it works after changing the package_type to library. so，does the package_type application mean that the -l option will not be generated? And, only projects that contain only executable and no any library files set to application?

[memsharded]

Package-type affects how information is propagated to consumers. If you have an application that requires a static-library, and someone does a requires to the application (in most cases it should be a tool_requires if intended to be used in the build), then the library information will not be propagated to the downstream consumers, only to the application.

Yes, in general, packages containing headers and libraries should be set to library if using options.shared or static-library/shared-library, even if they contain executables too. Packages that contain an executable only can be set to application.

[JamesPei]

@memsharded get it, thanks