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CMakeLists.txt详解

CMakeLists.txt是一个用于构建C/C++项目的CMake配置文件。它定义了项目的编译选项，包括编译器类型、依赖库、预处理宏和子目录等。让我们逐步解析这个文件。

编译器检测

CMAKE_CXX_COMPILER_ID 变量用于检测编译器类型。在这个示例中，如果编译器是Clang，则设置 CLANG 为true；如果编译器是GCC，则设置 GCC 为true。这样可以根据不同的编译器类型设置相关选项。

编译选项

CMakeLists.txt 文件中定义了一系列的编译选项，例如：

• WARNINGS_AS_ERRORS：将警告作为错误处理，如果启用此选项，则在编译过程中遇到任何警告都会导致构建失败。
• FILTER、ENCODER、DECODER、MUXER、DEMUXER：这些选项控制是否编译对应的过滤器、编码器、解码器、复用器和解复用器模块。
• ROCKFACE、ROCKX、RKNN：这些选项控制是否编译rockface、rockx和rknn封装模块。
• SANITIZER_STATIC、SANITIZER_DYNAMIC：这些选项用于在编译时启用地址和内存错误的静态或动态库。
• RKMEDIA_SOCKET：启用RKMedia套接字支持。

依赖库

CMakeLists.txt 文件使用 pkg_check_modules 函数查找并设置依赖库。示例中使用了 LIBDRM 和 LIBION 库。如果找到了这些库，则相应地设置预处理宏，并包含相关的头文件。

子目录

CMakeLists.txt 文件根据选项编译不同的子目录，包括 src 和 examples。在这些子目录中，可以编写项目源代码文件和示例代码，并设置链接库和其他编译选项。

其他配置

除了上述内容，CMakeLists.txt 文件还设置了一些其他配置，如设置编译器选项（C++11标准、禁用RTTI等）、预定义目标文件夹等。

下面是示例代码

#
# Copyright 2019 Fuzhou Rockchip Electronics Co., Ltd. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
## vi: set noexpandtab syntax=cmake:message(STATUS "cmake version ${CMAKE_VERSION}")
if(NOT CMAKE_VERSION VERSION_LESS "2.8.12.20131121")cmake_policy(SET CMP0025 OLD) # report Apple's Clang as just Clangcmake_policy(SET CMP0042 OLD) # do not require MACOSX_RPATH
endif()# Search packages for host system instead of packages for target system in case
# of cross compilation these macro should be defined by toolchain file
if(NOT COMMAND find_host_package)macro(find_host_package)find_package(${ARGN})endmacro()
endif()
if(NOT COMMAND find_host_program)macro(find_host_program)find_program(${ARGN})endmacro()
endif()list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")project(easymedia)cmake_minimum_required(VERSION 3.1.0 FATAL_ERROR)
include(CheckIncludeFiles)
include(CheckFunctionExists)
include(CheckSymbolExists)
include(CheckCXXCompilerFlag)# ----------------------------------------------------------------------------
# set property to classify library kinds
# ----------------------------------------------------------------------------
set_property(GLOBAL PROPERTY USE_FOLDERS ON)
set_property(GLOBAL PROPERTY PREDEFINED_TARGETS_FOLDER "CMakeTargets")# ----------------------------------------------------------------------------
# Compiler detection
# ----------------------------------------------------------------------------
if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")set(CLANG true)
endif()
if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")set(GCC true)
endif()if(CLANG)# treat clang roughly like gccset(GCC true)add_definitions(-Wall-Wextra-Wshadow-ffast-math)
elseif(CMAKE_COMPILER_IS_GNUCXX)add_definitions(-Wall-Wextra-Wshadow-ffast-math)check_cxx_compiler_flag(-Wno-narrowing GCC_HAS_NO_NARROWING)check_cxx_compiler_flag(-mstackrealign GCC_HAS_STACK_REALIGN)if(GCC_HAS_STACK_REALIGN)add_definitions(-mstackrealign)endif()execute_process(COMMAND ${CMAKE_CXX_COMPILER} -dumpversionOUTPUT_VARIABLE GCC_VERSION)
endif()if(${CMAKE_BUILD_TYPE} MATCHES "Release")set(CMAKE_C_VISIBILITY_PRESET hidden)set(CMAKE_CXX_VISIBILITY_PRESET hidden)
endif()# set c++11
set(CMAKE_CXX_STANDARD 11)
# rtti may be expensive on Embedded Platform, obey Google C++ Style Guide
# add_definitions(-fno-rtti)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")# add PIC flag
add_definitions(-fPIC)
# set (CMAKE_SHARED_LINKER_FLAGS ${CMAKE_EXE_LINKER_FLAGS})# add_definitions(-fvisibility=hidden -fvisibility-inlines-hidden)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility=hidden -fvisibility-inlines-hidden")
include_directories(./)if(USE_RKAIQ)find_package(RkAiq REQUIRED)include_directories(${RKAIQ_INCLUDE_DIRS})add_definitions(-DRKAIQ)
endif()if(AUDIO_ALGORITHM)add_definitions(-DAUDIO_ALGORITHM_ENABLE)
endif()# ----------------------------------------------------------------------------
# Build options
# ----------------------------------------------------------------------------
find_package(PkgConfig)
include(GNUInstallDirs)# ----------------------------------------------------------------------------
# Set Warning as Error
# ----------------------------------------------------------------------------
option(WARNINGS_AS_ERRORS "Stop compiles on first warning" OFF)
if(WARNINGS_AS_ERRORS)if(GCC)add_definitions(-Werror)elseif(MSVC)add_definitions(/WX)endif()
endif(WARNINGS_AS_ERRORS)option(FILTER "compile: filter" ON)
option(ENCODER "compile: encoder" ON)
option(DECODER "compile: decoder" ON)
option(MUXER "compile: muxer" ON)
option(DEMUXER "compile: demuxer" ON)
option(RKNN "compile: rknn wrapper" OFF)
option(ROCKFACE "compile: rockface wrapper" OFF)
option(ROCKX "compile: rockx wrapper" OFF)option(SANITIZER_STATIC "compile with sanitizer (static library linker)" OFF)
if(SANITIZER_STATIC)add_definitions(-fsanitize=address -static-libasan -g -ggdb -gdwarf -funwind-tables -rdynamic -O0)add_definitions(-fno-stack-protector -fno-omit-frame-pointer -fsanitize-recover=address)# add_definitions(-fsanitize=undefined)link_libraries(libasan.a dl m rt)
endif()option(SANITIZER_DYNAMIC "compile with sanitizer (dynamic library linker)" OFF)
if(SANITIZER_DYNAMIC)# NOTE: copy libasan.so with manual operationadd_definitions(-fsanitize=address -g -ggdb -gdwarf -funwind-tables -rdynamic -O0)add_definitions(-fno-stack-protector -fno-omit-frame-pointer -fsanitize-recover=address)# add_definitions(-fsanitize=undefined)link_libraries(asan)
endif()pkg_check_modules(LIBDRM libdrm)
if(LIBDRM_FOUND)add_definitions(-DLIBDRM)include_directories(${LIBDRM_INCLUDE_DIRS})set(EASY_MEDIA_DEPENDENT_LIBS drm)
else()
pkg_check_modules(LIBION libion)
if(LIBION_FOUND)add_definitions(-DLIBION)include_directories(${LIBION_INCLUDE_DIRS})set(EASY_MEDIA_DEPENDENT_LIBS ion)
endif()
endif()option(RKMEDIA_SOCKET "Enable rkmedia socket" OFF)
if(RKMEDIA_SOCKET)
add_definitions(-DRKMEDIA_SOCKET)
endif()if (MINILOGGER)
find_package(MiniLogger REQUIRED)
set(EASY_MEDIA_DEPENDENT_LIBS${EASY_MEDIA_DEPENDENT_LIBS} MiniLogger::MiniLogger)
add_definitions(-DRKMEDIA_SUPPORT_MINILOG)
endif()option(TIMESTAMP_DEBUG "Time-consuming statistics of each stage of MB" OFF)
if (TIMESTAMP_DEBUG)add_definitions(-DRKMEDIA_TIMESTAMP_DEBUG)
endif()option(COMPILES_MINIMEDIA "Enable compiles minimedia" OFF)
include_directories(include/easymedia)
include_directories(include/rkmedia)
add_subdirectory(src)option(COMPILES_EXAMPLES "Enable compiles examples" OFF)
if(COMPILES_EXAMPLES)include(CTest)enable_testing()add_subdirectory(examples)
endif()option(COMPILES_UVC_EXAMPLE "Enable compiles uvc example" OFF)