你还在学CMake的过程中毫无头绪吗？你还在为复杂程序库依赖发愁吗？你是否觉得原生CMake的编写冗余而低效？那就快来学习和使用PICMake吧！只需要一行，无论是可执行，动态库还是静态库，轻松搞定！同时高效支持多目标，复杂库的编译安装，从此告别大量冗余CMake代码，专注开发核心应用程序，编译不再愁！ 例如下面是使用PICMake编译一个依赖OpenGL的可执行文件，只需要一行！（第一行是加载PICMake，好吧，如果也要算那就是两行）：
include(PICMake)
pi_add_target(demo BIN src main.cpp REQUIRED OpenGL)
从此告别一堆罗嗦的find_package和其他冗余代码！
那么如何做到的呢？这一切的秘密都在PICMake.cmake这一个文件中哦,稍微啃一啃这个代码，绝对瞬间提高你对CMake的认识水平哦～好啦好啦，源码我们留给大家自己去深究，小编先给大家介绍PICMake的使用吧！
注释： 由于CMake仍然有很多弹性，不够统一的风格可能导致相互之间的支持较差，因此导致用户的工作量增大。 可以认为PICMake其实是规定了一个使用CMake的标准,当用户按照此标准来使用CMake时，可以大大简化工作流程。PICMake目前主要针对Linux下的C++工程，目前主要集成了CV领域的常用库支持，我们将持续对其进行改进更新，也欢迎更多开发者提出更多的意见！
好啦好啦，安装PICMake与使用CMake的过程完全一致，相信编译过CMake项目的娃子们一定不会陌生（嘿嘿～～），同时我们也建议大家使用下面的习惯来编译CMake项目哦：
mkdir build
cd build
cmake ..
make
sudo make install
实际上，PICMake本身核心只有一个文件，那就是cmake目录下面的那个，用户可以直接将它放在自己的项目中！为了让大家了解到PICMake的使用方式，我们把项目本身设计成了一个cmake工程，工程本身就是一个使用的例子哦～
对于安装后的PICMake，可使用sudo make uninstall 进行卸载，不要问我卸载是在哪里支持的，这是PICMake的秘密～～
PICMake的目录结构如下：
+- PICMake
++- CMakeLists -- PICMake安装文件与库示例
++- README.md -- PICMake介绍文件
++- cmake -- cmake相关
+++- PICMake.cmake.in -- 安装支持文件
+++- PICMake.cmake -- PICMake的主体文档
+++- CMake.md -- CMake学习文档
+++- learn -- 辅助学习的文件夹
+++- Find*.cmake -- 依赖包寻找脚本
++- src -- 库框架示例
++- examples -- 使用示例
在前面我们已经简单提到，使用PICMake只需要一行即可完成可执行和库编译，而实际上我们建议在加上固定的两行，标准的写法应该如下(例子详见examples/0_simple_app)：
cmake_minimum_required(VERSION 2.8) # 添加原因： 新版本的cmake规定第一行应该声明版本需求
include(PICMake) # 加载PICMake支持，也可以直接include(cmake/PICMake.cmake)
pi_add_target(simple_library SHARED showImage.cpp REQUIRED OpenCV)# 编译依赖OpenCV的简单库
pi_report_target() # 添加原因： PICMake建议加上用于报告最终将被编译的目标
可以看到添加的两行基本上是比较固定的，第一行是CMake的规定，最后一行是用于报告将会被编译的目标文件。
这里用到的一个核心函数是pi_add_target,其用法是:
pi_add_target(<name> <BIN/STATIC/SHARED> <src1/dir1 ...> [MODULES module1 ...] [REQUIRED module1 ...] [DEPENDENCY target1 ...])
第一个参数是目标名称，第二个参数是编译目标类型，第三个参数是要添加的源文件或文件夹，MODULES代表的是非必须第三方库列表，程序里可通过#ifdef HAS_QT宏选择性编译相关代码，REQUIRED代表必须的第三方库列表, DEPENDENCY代表当前目标所依赖的target。
对于较大一些的工程，往往包含多个目标和库，同时可能包含需要安装的目标，而本项目本身就展示了这样一个工程的PICMake写法（详见本工程"CMakeLists.txt")：
cmake_minimum_required(VERSION 2.6)
project(PICMake)
include(${CMAKE_CURRENT_LIST_DIR}/cmake/PICMake.cmake)# Use PICMake
if(FALSE) # Tree style
add_subdirectory(src)
else() # All in one
pi_add_target(StaticLibDemo STATIC src/StaticLibDemo) # 静态库示例
pi_add_target(SharedLibDemo SHARED src/SharedLibDemo) # 动态库示例
pi_add_target(AppDemo BIN src/AppDemo DEPENDENCY StaticLibDemo SharedLibDemo REQUIRED OpenCV) # 依赖前两个库的可执行文件
pi_add_target(ConditionalApp BIN src/ConditionalApp MODULES PIL Qt System REQUIRED OpenCV) #条件编译示例
endif()
pi_install(CMAKE ${PROJECT_SOURCE_DIR}/cmake/PICMake.cmake.in)# 安装文件示例，其中自动支持卸载
pi_report_target()
这里添加了一个pi_install函数，其详细用法为：
pi_install([HEADERS header1/dir1 ...] [TARGETS target1 ...] [CMAKE cmake_config] [BIN_DESTINATION dir] [LIB_DESTINATION dir] [HEADER_DESTINATION dir])
对于MODULES和REQUIRED中设定的每一个PACKAGE，PICMake都会调用find_package函数去寻找对应的FindPackge.cmake文档。其中FindPackage.cmake文档需要去寻找PACKAGE的头文件路径和库文件模块。
下表列出了FindPackage的主要输入变量：
| 变量名 | 变量说明 |
|---|---|
| PACKAGE_FIND_NAME | 需要寻找的包名字 |
| PACKAGE_FIND_VERSION | 需要寻找的包版本 |
| PACKAGE_FIND_VERSION_MAJOR | 需要寻找的主版本号 |
| PACKAGE_FIND_VERSION_MINOR | 需要寻找的次版本号 |
| PACKAGE_FIND_VERSION_PATCH | 需要寻找的版本补丁号 |
| PACKAGE_FIND_COMPONENTS | 需要寻找的组件 |
对于指令find_package(PIL 1.1.0 REQUIRED base cv）， PIL_FIND_NAME即为PIL， PIL_FIND_VERSION为1.1.0， 其中PIL_FIND_VERSION_MAJOR为1, PIL_FIND_VERSION_MINOR为1, PIL_FIND_VERSION_PATCH为0， PIL_FIND_COMPONENTS为base和cv。
下表列出了FindPackage.cmake中需要给定的一些参数：
| 变量名 | 变量说明 |
|---|---|
| PACKAGE_FOUND | 判断包PACKAGE是否被成功找到（TRUE,FALSE) |
| PACKAGE_VERSION | 返回包PACKAGE的版本号字符串 |
| PACKAGE_VERSION_MAJOR | 查找到的主版本号 |
| PACKAGE_VERSION_MINOR | 查找到的次版本号 |
| PACKAGE_VERSION_PATCH | 查找到的版本补丁号 |
| PACKAGE_INCLUDES | 同PACKAGE_INCLUDE_DIR,返回包的头文件地址 |
| PACKAGE_LIBRARIES | 同PACKAGE_LIBRARY,PACKAGE_LIBS，返回包的库依赖 |
| PACKAGE_DEFINITIONS | 返回包中需要的预编译定义 |
其详细实现可参考FindPIL.cmake。
| 函数（宏）名 | 函数说明 |
|---|---|
pi_collect_packagenames(<RESULT_NAME> [VERBOSE] [path1 ...]) |
Collect all available packages from "Find*.cmake" files and put the result to RESULT_NAME. |
pi_removesource(<VAR_NAME> <regex>) |
Remove all source files with name matches <regex>. |
pi_hasmainfunc(<RESULT_NAME> source1 ...) |
Look for the source files with main function. |
pi_add_target(<name> <BIN/STATIC/SHARED> <src1/dir1 ...> [MODULES module1 ...] [REQUIRED module1 ...] [DEPENDENCY target1 ...]) |
A combination of add_executable , add_library, add_definitions and target_link_libraries, MODULES includes packges or targets inessential and REQUIRED includes packages or target required,DEPENDENCY is used to include targets not defined and will be added after. |
pi_add_targets([name1 ...]) |
Add one or more targets, if one, please set TARGET_NAME, TARGET_TYPE, TARGET_SRCS, TARGET_MODULES, TARGET_REQUIRED and so on. If more than one target, replace TARGET with ${TARGET_NAME}. |
pi_report_target([LIBS2COMPILE] [APPS2COMPILE]) |
Report all targets added. |
pi_install([HEADERS header1/dir1 ...] [TARGETS target1 ...] [CMAKE cmake_config] [BIN_DESTINATION dir] [LIB_DESTINATION dir] [HEADER_DESTINATION dir]) |
A combination of multi install commands and auto support make install and make uninstall. |
pi_collect_packages(<RESULT_NAME> [VERBOSE] [MODULES package1 ...] [REQUIRED package1 package2 ...]) |
Find multi packages with find_package() and collect available packages to RESULT_NAME. All packages will be checked and once with VERBOSE ON, all information will be reported. |
pi_check_modules(module1 [module2 ...]) |
Let module name to upper and make valid _FOUND, _INCLUDES, _LIBRARIES, _DEFINITIONS. |
pi_report_modules(module1 [module2 ...]) |
Report packages information summary. |
| 变量名 | 变量说明 |
|---|---|
| PROJECT_NAME | 返回通过PROJECT指令定义的项目名称 |
| PROJECT_SOURCE_DIR | CMake源码地址，即cmake命令后指定的地址 |
| PROJECT_BINARY_DIR | 运行cmake命令的目录,通常是PROJECT_SOURCE_DIR下的build目录 |
| CMAKE_MODULE_PATH | 定义自己的cmake模块所在的路径 |
| CMAKE_CURRENT_SOURCE_DIR | 当前处理的CMakeLists.txt所在的路径 |
| CMAKE_CURRENT_LIST_DIR | 当前文件夹路径 |
| CMAKE_CURRENT_LIST_FILE | 输出调用这个变量的CMakeLists.txt的完整路径 |
| CMAKE_CURRENT_LIST_LINE | 输出这个变量所在的行 |
| CMAKE_RUNTIME_OUTPUT_DIRECTORY | 生成可执行文件路径 |
| CMAKE_LIBRARY_OUTPUT_DIRECTORY | 生成库的文件夹路径 |
| CMAKE_BUILD_TYPE | 指定基于make的产生器的构建类型（Release，Debug） |
| CMAKE_C_FLAGS | *.C文件编译选项，如 -std=c99 -O3 -march=native |
| CMAKE_CXX_FLAGS | *.CPP文件编译选项，如 -std=c++11 -O3 -march=native |
| CMAKE_CURRENT_BINARY_DIR | target编译目录 |
| CMAKE_INCLUDE_PATH | 环境变量,非cmake变量 |
| CMAKE_LIBRARY_PATH | 环境变量 |
| CMAKE_STATIC_LIBRARY_PREFIX | 静态库前缀, Linux下默认为lib |
| CMAKE_STATIC_LIBRARY_SUFFIX | 静态库后缀，Linux下默认为.a |
| CMAKE_SHARED_LIBRARY_PREFIX | 动态库前缀，Linux下默认为lib |
| CMAKE_SHARED_LIBRARY_SUFFIX | 动态库后缀，Linux下默认为.so |
| BUILD_SHARED_LIBS | 如果为ON，则add_library默认创建共享库 |
| CMAKE_INSTALL_PREFIX | 配置安装路径，默认为/usr/local |
| CMAKE_ABSOLUTE_DESTINATION_FILES | 安装文件列表时使用ABSOLUTE DESTINATION 路径 |
| CMAKE_AUTOMOC_RELAXED_MODE | 在严格和宽松的automoc模式间切换 |
| CMAKE_BACKWARDS_COMPATIBILITY | 构建工程所需要的CMake版本 |
| CMAKE_COLOR_MAKEFILE | 开启时，使用Makefile产生器会产生彩色输出 |
| CMAKE_ALLOW_LOOSE_LOOP_CONSTRUCTS | 用来控制IF ELSE语句的书写方式 |
| 命令名 |
|---|
project(<PROJECT-NAME> [LANGUAGES] [<language-name>...])project(<PROJECT-NAME> [VERSION <major>[.<minor>[.<patch>[.<tweak>]]]] [LANGUAGES <language-name>...]) |
set(<variable> <value> [[CACHE <type> <docstring> [FORCE]] | PARENT_SCOPE]) set(<variable> <value1> ... <valueN>) |
unset(<variable> [CACHE | PARENT_SCOPE]) unset(ENV{LD_LIBRARY_PATH}) |
include(<file|module> [OPTIONAL] [RESULT_VARIABLE <VAR>] [NO_POLICY_SCOPE]) |
cmake_minimum_required(VERSION major[.minor[.patch[.tweak]]] [FATAL_ERROR])cmake_policy(VERSION major[.minor[.patch[.tweak]]]) |
message([<mode>] "message to display" ...) STATUS, WARNING, AUTHOR_WARNING， SEND_ERROR， FATAL_ERROR， DEPRECATION |
list(LENGTH <list> <output variable>)list(GET <list> <element index> [<element index> ...] <output variable>)list(APPEND <list> [<element> ...])list(FIND <list> <value> <output variable>)list(INSERT <list> <element_index> <element> [<element> ...])list(REMOVE_ITEM <list> <value> [<value> ...])list(REMOVE_AT <list> <index> [<index> ...])list(REMOVE_DUPLICATES <list>)list(REVERSE <list>)list(SORT <list>) |
include_directories([AFTER|BEFORE] [SYSTEM] dir1 [dir2 ...]) |
file(WRITE filename "message to write"... )file(APPEND filename "message to write"... )file(READ filename variable [LIMIT numBytes] [OFFSET offset] [HEX])file(<MD5|SHA1|SHA224|SHA256|SHA384|SHA512> filename variable)file(STRINGS filename variable [LIMIT_COUNT num] [LIMIT_INPUT numBytes] [LIMIT_OUTPUT numBytes] [LENGTH_MINIMUM numBytes] [LENGTH_MAXIMUM numBytes] [NEWLINE_CONSUME] [REGEX regex] [NO_HEX_CONVERSION])file(GLOB variable [RELATIVE path] [globbing expressions]...)file(GLOB_RECURSE variable [RELATIVE path] [FOLLOW_SYMLINKS] [globbing expressions]...)file(RENAME <oldname> <newname>)file(REMOVE [file1 ...])file(REMOVE_RECURSE [file1 ...])file(MAKE_DIRECTORY [directory1 directory2 ...])file(RELATIVE_PATH variable directory file)file(TO_CMAKE_PATH path result)file(TO_NATIVE_PATH path result)file(DOWNLOAD url file [INACTIVITY_TIMEOUT timeout] [TIMEOUT timeout] [STATUS status] [LOG log] [SHOW_PROGRESS] [EXPECTED_HASH ALGO=value] [EXPECTED_MD5 sum] [TLS_VERIFY on|off] [TLS_CAINFO file])file(UPLOAD filename url [INACTIVITY_TIMEOUT timeout] [TIMEOUT timeout] [STATUS status] [LOG log] [SHOW_PROGRESS])file(TIMESTAMP filename variable [<format string>] [UTC])file(GENERATE OUTPUT output_file <INPUT input_file|CONTENT input_content> [CONDITION expression]) |
get_filename_component(<VAR> <FileName> <COMP> [CACHE])DIRECTORY = Directory without file nameNAME = File name without directoryEXT = File name longest extension (.b.c from d/a.b.c)NAME_WE = File name without directory or longest extensionABSOLUTE = Full path to fileREALPATH = Full path to existing file with symlinks resolvedPATH = Legacy alias for DIRECTORY (use for CMake <= 2.8.11) |
string(REGEX MATCH <regular_expression> <output variable> <input> [<input>...])string(REGEX MATCHALL <regular_expression> <output variable> <input> [<input>...])string(REGEX REPLACE <regular_expression> <replace_expression> <output variable> <input> [<input>...])string(REPLACE <match_string> <replace_string> <output variable> <input> [<input>...])string(CONCAT <output variable> [<input>...])string(<MD5|SHA1|SHA224|SHA256|SHA384|SHA512> <output variable> <input>)string(COMPARE EQUAL <string1> <string2> <output variable>)string(COMPARE NOTEQUAL <string1> <string2> <output variable>)string(COMPARE LESS <string1> <string2> <output variable>)string(COMPARE GREATER <string1> <string2> <output variable>)string(ASCII <number> [<number> ...] <output variable>)string(CONFIGURE <string1> <output variable> [@ONLY] [ESCAPE_QUOTES])string(TOUPPER <string1> <output variable>)string(TOLOWER <string1> <output variable>)string(LENGTH <string> <output variable>)string(SUBSTRING <string> <begin> <length> <output variable>)string(STRIP <string> <output variable>)string(RANDOM [LENGTH <length>] [ALPHABET <alphabet>] [RANDOM_SEED <seed>] <output variable>)string(FIND <string> <substring> <output variable> [REVERSE])string(TIMESTAMP <output variable> [<format string>] [UTC])string(MAKE_C_IDENTIFIER <input string> <output variable>) |
add_executable(<name> [WIN32] [MACOSX_BUNDLE] [EXCLUDE_FROM_ALL] source1 [source2 ...])add_executable(<name> IMPORTED [GLOBAL])add_executable(<name> ALIAS <target>) |
add_library(<name> [STATIC | SHARED | MODULE] [EXCLUDE_FROM_ALL] source1 [source2 ...])add_library(<name> <SHARED|STATIC|MODULE|UNKNOWN> IMPORTED [GLOBAL])add_library(<name> OBJECT <src>...)add_library(<name> ALIAS <target>)add_library(<name> INTERFACE [IMPORTED [GLOBAL]]) |
target_link_libraries(<target> [item1 [item2 [...]]] [[debug|optimized|general] <item>] ...)target_link_libraries(<target> <PRIVATE|PUBLIC|INTERFACE> <lib> ... [<PRIVATE|PUBLIC|INTERFACE> <lib> ... ] ...]) |
find_package(<package> [version] [EXACT] [QUIET] [MODULE]
[REQUIRED] [[COMPONENTS] [components...]]
[OPTIONAL_COMPONENTS components...]
[NO_POLICY_SCOPE])
set_property(<GLOBAL |
DIRECTORY [dir] |
TARGET [target1 [target2 ...]] |
SOURCE [src1 [src2 ...]] |
TEST [test1 [test2 ...]] |
CACHE [entry1 [entry2 ...]]>
[APPEND] [APPEND_STRING]
PROPERTY <name> [value1 [value2 ...]])
get_property(<variable>
<GLOBAL |
DIRECTORY [dir] |
TARGET <target> |
SOURCE <source> |
TEST <test> |
CACHE <entry> |
VARIABLE>
PROPERTY <name>
[SET | DEFINED | BRIEF_DOCS | FULL_DOCS])
add_subdirectory(source_dir [binary_dir]
[EXCLUDE_FROM_ALL])
- set(Foo a b c)
- set(Foo "a b c")
- $ENV{VAR}
- set(ENV{VAR} /home}
True if the constant is 1, ON, YES, TRUE, Y, or a non-zero number. False if the constant is 0, OFF, NO, FALSE, N, IGNORE, NOTFOUND, the empty string, or ends in the suffix -NOTFOUND. Named boolean constants are case-insensitive. If the argument is not one of these constants, it is treated as a variable.
判断表达式中常用的指令:
| 命令名 | 变量说明 |
|---|---|
| NOT | True if the expression is not true |
| AND | True if both expressions would be considered true individually |
| OR | True if either expression would be considered true individually |
| COMMAND | True if the given name is a command, macro or function that can be invoked |
| POLICY | True if the given name is an existing policy |
| TARGET | True if the given name is an existing logical target name such as those created by the add_executable(), add_library(), or add_custom_target() commands} |
| EXISTS | True if the named file or directory exists. Behavior is well-defined only for full paths |
| IS_DIRECTORY | True if the given name is a directory. Behavior is well-defined only for full paths |
| IS_SYMLINK | True if the given name is a symbolic link. Behavior is well-defined only for full paths |
| IS_ABSOLUTE | True if the given path is an absolute path |
| MATCHES | if(<variable|string> MATCHES regex) True if the given string or variable’s value matches the given regular expression |
| LESS | True if the given string or variable’s value is a valid number and less than that on the right |
| GREATER | True if the given string or variable’s value is a valid number and greater than that on the right |
| EQUAL | True if the given string or variable’s value is a valid number and equal to that on the right |
| STRLESS | True if the given string or variable’s value is lexicographically less than the string or variable on the right |
| STRGREATER | True if the given string or variable’s value is lexicographically greater than the string or variable on the right |
| STREQUAL | True if the given string or variable’s value is lexicographically equal to the string or variable on the right |
| VERSION_LESS | Component-wise integer version number comparison (version format is major[.minor[.patch[.tweak]]] |
| VERSION_EQUAL | Component-wise integer version number comparison (version format is major[.minor[.patch[.tweak]]]) |
| VERSION_GREATER | Component-wise integer version number comparison (version format is major[.minor[.patch[.tweak]]]) |
| DEFINED | True if the given variable is defined. It does not matter if the variable is true or false just if it has been set. (Note macro arguments are not variables.) |
函数可以返回，可以用 return()命令返回。如果要从函数中返回值，只能通过参数返回：
#定义函数 get_lib从给定的目录查找指定的库，并把它传回到参数 lib_FILE中
function(get_lib lib_FILE lib_NAME lib_PATH)
#message("lib_name:""${lib_NAME}")
set(__LIB "__LIB-NOTFOUND")
#message("__LIB:""${__LIB}")
find_library(__LIB ${lib_NAME} ${lib_PATH})
if(__LIB STREQUAL "__LIB-NOTFOUND")
message("don't find ${lib_NAME} librarys in ${lib_PATH}")
return()
endif()
#message("__LIB:""${__LIB}")
set(${lib_FILE} ${__LIB}PARENT_SCOPE)
endfunction(get_lib)
set命令中 PARENT_SCOPE表示传递给函数调用者所拥有的变量