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CMake Basic Notes

Basic Build System​

Build for executable:

cmake_minimum_required(VERSION 2.8.9)
project(directory_test)

add_definitions(-DUSEXX)
add_compile_options(-std=c++11 -Wall -Wextra)

# Bring the headers, such as Student.h into the project
include_directories(include)

# Can manually add the sources using the set command as follows:
# set(SOURCES src/mainApp.cpp src/Student.cpp)

# However, the file(GLOB...) allows for wildcard additions:
file(GLOB SOURCES "src/*.cpp")

message(STATUS "CMake demo: build for executable")

add_executable(testStudent ${SOURCES})

build for library

cmake_minimum_required(VERSION 2.8.9)
project(directory_test)
set(CMAKE_BUILD_TYPE Release)

# Bring the headers, such as Student.h into the project
include_directories(include)

# However, the file(GLOB...) allows for wildcard additions:
file(GLOB SOURCES "src/*.cpp")

# Generate the shared library from the sources
# flag: SHARED, STATIC, MODULE
add_library(testStudent SHARED ${SOURCES})

message(STATUS "CMake demo: build for library")

# Set the location for library installation -- i.e., /usr/lib in this case
# not really necessary in this example. Use "sudo make install" to apply
install(TARGETS testStudent DESTINATION /usr/lib)

use a shared or static library

cmake_minimum_required(VERSION 2.8.9)
project(TestLibrary)

# For the shared library:
set(PROJECT_LINK_LIBS libTestStudent.so)
link_directories(~/exploringBB/extras/cmake/studentLib_shared/build)

# For the static library:
# set (PROJECT_LINK_LIBS libTestStudent.a)
# link_directories(~/exploringBB/extras/cmake/studentLib_static/build)

include_directories(~/exploringBB/extras/cmake/studentLib_shared/include)

add_executable(libTest libTest.cpp)
target_link_libraries(libTest ${PROJECT_LINK_LIBS} )

message(STATUS "CMake demo: use library")

set output of library

# 指定lib输出目录
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)

# 指定版本
set(DEMO5_VERSION_MAJOR 1)
set(DEMO5_VERSION_MINOR 1)
set(DEMO5_VERSION_PATCH 1)
set(DEMO5_VERSION ${DEMO5_VERSION_MAJOR}.${DEMO5_VERSION_MINOR}.${DEMO5_VERSION_PATCH})

aux_source_directory(. SRC_LIST)

add_library(demo5 SHARED ${SRC_LIST})
set_target_properties(
    demo5 PROPERTIES
    VERSION ${DEMO5_VERSION}
    SOVERSION ${DEMO5_VERSION_MAJOR}
)

build for library and executable

cmake_minimum_required(VERSION 3.5)
project(MiniSat VERSION 2.2 LANGUAGES CXX)

add_library(libMiniSat STATIC
    miniSat/core/Solver.cc
    miniSat/utils/Options.cc
    miniSat/utils/System.cc
    miniSat/simp/SimpSolver.cc
)

target_compile_features(libMiniSat
    PUBLIC
      cxx_attributes
      cxx_defaulted_functions
      cxx_deleted_functions
      cxx_final
)

target_include_directories(libMiniSat PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})

target_compile_definitions(libMiniSat PUBLIC __STDC_LIMIT_MACROS __STDC_FORMAT_MACROS)

# Also build the two MiniSat executables
add_executable(miniSat miniSat/core/Main.cc)
target_link_libraries(miniSat libMiniSat)

add_executable(miniSat-simp miniSat/simp/Main.cc)
target_link_libraries(miniSat-simp libMiniSat)

Basic Options​

make VERBOSE=1

Standard options:

  • -DCMAKE_BUILD_TYPE= Pick from Release, RelWithDebInfo, Debug, or sometimes more
  • -DCMAKE_INSTALL_PREFIX= /usr/local (the default), ~/.local
  • -D BUILD_SHARED_LIBS=
  • --trace print every line of CMake

Flow Control​

if control​

  • Unary: NOT, TARGET, EXISTS (file), DEFINED
  • Binary: STREQUAL, AND, OR, MATCHES(regular expression), VERSION_LESS, VERSION_LESS_EQUAL
if(WIN32)
    message("This is win32 platform")
else()
    message("This is not win32 platform")
endif()

foreach control​

set(FOR_LIST demo1.cpp demo2.cpp demo3.cpp)
foreach(f ${FOR_LIST})
    message("now is file: " ${f})
endforeach ()

while control​

set(A "1")
set(B "1")
while(A LESS "1000000")
    message("${A}")                 # Print A
    math(EXPR T "${A} + ${B}")      # Add values of A and B; store result in T
    set(A "${B}")                   # Assign the value of B to A
    set(B "${T}")                   # Assign the value of T to B
endwhile()

function control​

Basic Usage of Function​

function(doubleIt VALUE)
    math(EXPR RESULT "${VALUE} * 2")
    message("${RESULT}")
endfunction()

doubleIt("4")          # Prints: 8
function(doubleIt VARNAME VALUE)
    math(EXPR RESULT "${VALUE} * 2")
    set(${VARNAME} "${RESULT}" PARENT_SCOPE)
endfunction()

doubleIt(RESULT "4")   # Tell the function to set the variable named RESULT
message("${RESULT}")   # Prints: 8
function(doubleEach)
    foreach(ARG ${ARGN})           # Iterate over each argument
        math(EXPR N "${ARG} * 2")  # Double ARG numeric value
        message("${N}")            # Print N
    endforeach()
endfunction()

doubleEach(5 6 7 8)                # Prints 10, 12, 14, 16 on separate lines

Parse Arguments of Function​

function(COMPLEX)
cmake_parse_arguments(
    COMPLEX_PREFIX
    "SINGLE;ANOTHER"
    "ONE_VALUE;ALSO_ONE_VALUE"
    "MULTI_VALUES"
    ${ARGN}
)

endfunction()

complex(SINGLE ONE_VALUE value MULTI_VALUES some other values)

Inside the function after this call, you'll find:

COMPLEX_PREFIX_SINGLE = TRUE
COMPLEX_PREFIX_ANOTHER = FALSE
COMPLEX_PREFIX_ONE_VALUE = "value"
COMPLEX_PREFIX_ALSO_ONE_VALUE = <UNDEFINED>
COMPLEX_PREFIX_MULTI_VALUES = "some;other;values"

Useful Command​

Checking Command​

# does this system provide the log and exp functions?
include(CheckFunctionExists)
check_function_exists(log HAVE_LOG)
check_function_exists(exp HAVE_EXP)

Testing Command​

#define a macro to simplify adding tests, then use it
macro(do_test arg result)
  add_test(TutorialComp${arg} Tutorial ${arg})
  set_tests_properties(TutorialComp${arg}
    PROPERTIES PASS_REGULAR_EXPRESSION ${result})
endmacro(do_test)

# do a bunch of result based tests
do_test(25 "25 is 5")
do_test(-25 "-25 is 0")
include(CTest)

# does the application run
add_test (TutorialRuns Tutorial 25)

# does it sqrt of 25
add_test (TutorialComp25 Tutorial 25)
set_tests_properties (TutorialComp25 PROPERTIES PASS_REGULAR_EXPRESSION "25 is 5")

# does it handle negative numbers
add_test (TutorialNegative Tutorial -25)
set_tests_properties (
    TutorialNegative PROPERTIES
    PASS_REGULAR_EXPRESSION "-25 is 0"
)

# does it handle small numbers
add_test (TutorialSmall Tutorial 0.0001)
set_tests_properties (
    TutorialSmall PROPERTIES
    PASS_REGULAR_EXPRESSION "0.0001 is 0.01"
)

# does the usage message work?
add_test (TutorialUsage Tutorial)
set_tests_properties (
    TutorialUsage PROPERTIES
    PASS_REGULAR_EXPRESSION "Usage:.*number"
)

Option Command​

# 是否使用我们自己的函数？
option(USE_MATH
        "Use tutorial provided math implementation" ON)

# add the MathFunctions library?
if(USE_MATH)
  include_directories("${PROJECT_SOURCE_DIR}/MathFunctions")
  add_subdirectory(MathFunctions)
  set(EXTRA_LIBS ${EXTRA_LIBS} MathFunctions)
endif(USE_MATH)

# add the executable
add_executable(Tutorial tutorial.cxx)
target_link_libraries(Tutorial  ${EXTRA_LIBS})

Math Command​

set(ARGS "EXPR;T;1 + 1")
math(${ARGS})                      # Equivalent to calling math(EXPR T "1 + 1")

List Command​

set(MY_LIST These are separate arguments)
list(REMOVE_ITEM MY_LIST "separate")  # Removes "separate" from the list
message("${MY_LIST}")                 # Prints: These;are;arguments

Package Command​

# build a CPack driven installer package
include(InstallRequiredSystemLibraries)
set(CPACK_RESOURCE_FILE_LICENSE
     "${CMAKE_CURRENT_SOURCE_DIR}/License.txt")
set(CPACK_PACKAGE_VERSION_MAJOR "${Tutorial_VERSION_MAJOR}")
set(CPACK_PACKAGE_VERSION_MINOR "${Tutorial_VERSION_MINOR}")
include(CPack)
cpack --config CPackConfig.cmake
cpack --config CPackSourceConfig.cmake

Install Command​

install binaries​

INSTALL(TARGETS targets...
        [[ARCHIVE|LIBRARY|RUNTIME]
        [DESTINATION < dir >]
        [PERMISSIONS permissions...]
        [CONFIGURATIONS
        [Debug|Release|...]]
        [COMPONENT < component >]
        [OPTIONAL]
        ] [...])

INSTALL(TARGETS myRun myLib myStaticLib
        RUNTIME DESTINATION bin
        LIBRARY DESTINATION lib
        ARCHIVE DESTINATION libStatic）

install normal files​

INSTALL(FILES files... DESTINATION <dir>
     [PERMISSIONS permissions...]
     [CONFIGURATIONS [Debug|Release|...]]
     [COMPONENT <component>]
     [RENAME <name>] [OPTIONAL])

INSTALL(FILES COPYRIGHT README DESTINATION share/doc/cmake/t2)

install scripts​

INSTALL(PROGRAMS files... DESTINATION <dir>
     [PERMISSIONS permissions...]
     [CONFIGURATIONS [Debug|Release|...]]
     [COMPONENT <component>]
     [RENAME <name>] [OPTIONAL])

INSTALL(PROGRAMS runHello.sh DESTINATION bin)

install directories​

INSTALL(DIRECTORY dirs... DESTINATION <dir>
     [FILE_PERMISSIONS permissions...]
     [DIRECTORY_PERMISSIONS permissions...]
     [USE_SOURCE_PERMISSIONS]
     [CONFIGURATIONS [Debug|Release|...]]
     [COMPONENT <component>]
     [[PATTERN <pattern> | REGEX <regex>]
     [EXCLUDE] [PERMISSIONS permissions...]] [...])

INSTALL(DIRECTORY icons scripts/ DESTINATION share/myProj
     PATTERN "CVS" EXCLUDE
     PATTERN "scripts/*"
     PERMISSIONS OWNER_EXECUTE OWNER_WRITE OWNER_READ
     GROUP_EXECUTE GROUP_READ)

Install Demo​

find_package(Bar 2.0 REQUIRED)
add_library(Foo ...)
target_link_libraries(Foo PRIVATE Bar::Bar)

install(TARGETS Foo EXPORT FooTargets
  LIBRARY DESTINATION lib
  ARCHIVE DESTINATION lib
  RUNTIME DESTINATION bin
  INCLUDES DESTINATION include
)

install(EXPORT FooTargets
  FILE FooTargets.cmake
  NAMESPACE Foo::
  DESTINATION lib/cmake/Foo
)

find packages​

find modules

cmake –-help-module-list
ls /usr/share/cmake/Modules/

cmake --help-module FindBZip2

Basic Usage of Find​

project(helloWorld)
add_executable(helloWorld hello.c)
find_package (BZip2)
if (BZIP2_FOUND)
    include_directories(${BZIP_INCLUDE_DIRS})
    target_link_libraries(helloWorld ${BZIP2_LIBRARIES})
endif (BZIP2_FOUND)
find_path(Foo_INCLUDE_DIR foo.h)
find_library(Foo_LIBRARY foo)
mark_as_advanced(Foo_INCLUDE_DIR Foo_LIBRARY)

include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(Foo
  REQUIRED_VARS Foo_LIBRARY Foo_INCLUDE_DIR
)

if(Foo_FOUND AND NOT TARGET Foo::Foo)
  add_library(Foo::Foo UNKNOWN IMPORTED)
  set_target_properties(Foo::Foo PROPERTIES
    IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
    IMPORTED_LOCATION "${Foo_LIBRARY}"
    INTERFACE_INCLUDE_DIRECTORIES "${Foo_INCLUDE_DIR}"
  )
endif()

Find CMake​

Find.cmake: add find module for project

# cmake/FindDEMO9LIB.cmake
# 辅助输出信息
message("now using FindDEMO9LIB.cmake find demo9 lib")

# 将demo9.h文件路径赋值给DEMO9LIB_INCLUDE_DIR
FIND_PATH(DEMO9LIB_INCLUDE_DIR demo9.h /usr/include/demo9/
        /usr/local/demo9/include/)
message("./h dir ${DEMO9LIB_INCLUDE_DIR}")

# 将libDemo9_lib.a文件路径赋值给DEMO9LIB_LIBRARY
FIND_LIBRARY(DEMO9LIB_LIBRARY libDemo9_lib.a /usr/local/demo9/lib/)
message("lib dir: ${DEMO9LIB_LIBRARY}")

if(DEMO9LIB_INCLUDE_DIR AND DEMO9LIB_LIBRARY)
    # 设置变量结果
    set(DEMO9LIB_FOUND TRUE)
endif(DEMO9LIB_INCLUDE_DIR AND DEMO9LIB_LIBRARY)

Full Find Demo​

# CMakeLists.txt
cmake_minimum_required(VERSION 3.5)

project(demo9)

# create libDemo9_lib.a
set(SRC_LIB demo9.cpp)
add_library(demo9_lib STATIC ${SRC_LIB})

# install it
install(TARGETS demo9_lib DESTINATION demo9/lib)
install(FILES demo9.h DESTINATION demo9/include)

# create demo9_main executable
set(SRC_EXE demo9_main.cpp)

# set demo9_lib cmake module path
set(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)
message("cmake_module_path: ${CMAKE_MODULE_PATH}")
find_package(DEMO9LIB)

if(DEMO9LIB_FOUND)
    add_executable(demo9_main ${SRC_EXE})
    message("found demo9 ${DEMO9LIB_INCLUDE_DIR} ${DEMO9LIB_LIBRARY}")
    include_directories(${DEMO9LIB_INCLUDE_DIR})
    target_link_libraries(demo9_main ${DEMO9LIB_LIBRARY})
else()
    message("not found DEMO9LIB_FOUND")
endif(DEMO9LIB_FOUND)

Useful Tools​

ldd and ar

ldd library.so
ar -t library.a

Makefile

# -----------------------------------------------------------------------------
# CMake project wrapper Makefile ----------------------------------------------
# -----------------------------------------------------------------------------

SHELL := /bin/bash
RM    := rm -rf
MKDIR := mkdir -p

all: ./build/Makefile
    @ $(MAKE) -C build

./build/Makefile:
    @  ($(MKDIR) build > /dev/null)
    @  (cd build > /dev/null 2>&1 && cmake ..)

clean:
    @  ($(MKDIR) build > /dev/null)
    @  (cd build > /dev/null 2>&1 && cmake .. > /dev/null 2>&1)
    @- $(MAKE) --silent -C build clean || true
    @- $(RM) ./build/Makefile
    @- $(RM) ./build/src
    @- $(RM) ./build/test
    @- $(RM) ./build/CMake*
    @- $(RM) ./build/cmake.*
    @- $(RM) ./build/*.cmake
    @- $(RM) ./build/*.txt

ifeq ($(findstring clean,$(MAKECMDGOALS)),)
    $(MAKECMDGOALS): ./build/Makefile
    @ $(MAKE) -C build $(MAKECMDGOALS)
endif

Config Command​

Version Config​

cmake_minimum_required(VERSION 3.1)

if(${CMAKE_VERSION} VERSION_LESS 3.13)
  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
else()
  cmake_policy(VERSION 3.13)
endif()

Project Config​

project(MyProject VERSION 1.0 DESCRIPTION "Very nice project" LANGUAGES CXX)

Environment Config​

set(ENV{variable_name} value) and get $ENV{variable_name} environment variables

Library for Clients Usage​

include(CMakePackageConfigHelpers)
write_basic_package_version_file("FooConfigVersion.cmake"
  VERSION ${Foo_VERSION}
  COMPATIBILITY SameMajorVersion
)

install(FILES "FooConfig.cmake" "FooConfigVersion.cmake"
  DESTINATION lib/cmake/Foo
)
include(CMakeFindDependencyMacro)
find_dependency(Bar 2.0)
include("${CMAKE_CURRENT_LIST_DIR}/FooTargets.cmake")

Test Setting​

set(CTEST_SOURCE_DIRECTORY "/source")
set(CTEST_BINARY_DIRECTORY "/binary")

set(ENV{CXXFLAGS} "--coverage")
set(CTEST_CMAKE_GENERATOR "Ninja")
set(CTEST_USE_LAUNCHERS 1)

set(CTEST_COVERAGE_COMMAND "gcov")
set(CTEST_MEMORYCHECK_COMMAND "valgrind")
#set(CTEST_MEMORYCHECK_TYPE "ThreadSanitizer")

ctest_start("Continuous")
ctest_configure()
ctest_build()
ctest_test()
ctest_coverage()
ctest_memcheck()
ctest_submit()
macro(package_add_test TESTNAME)
    add_executable(${TESTNAME} ${ARGN})
    target_link_libraries(${TESTNAME} gtest gmock gtest_main)
    add_test(${TESTNAME} COMMAND ${TESTNAME})
    set_target_properties(${TESTNAME} PROPERTIES FOLDER tests)
endmacro()

package_add_test(test1 test1.cpp)

Generator Expression​

Most CMake commands happen at configure time, include the if statements seen above. Generator expressions were added at runtime. They are evaluated in target properties:

  • If you want to put a compile flag only for the DEBUG configuration
  • Limiting an item to a certain language only, such as CXX
  • Accessing configuration dependent properties, like target file location
  • Giving a different location for build and install directories
target_include_directories(MyTarget PUBLIC
  $<BUILD_INTERFACE:"${CMAKE_CURRENT_SOURCE_DIR}/include">
  $<INSTALL_INTERFACE:include>
)

Submodule and Dependencies​

find_package(Git QUIET)

if(GIT_FOUND AND EXISTS "${PROJECT_SOURCE_DIR}/.git")
  execute_process(COMMAND
    ${GIT_EXECUTABLE} submodule update --init --recursive
    WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} RESULT_VARIABLE GIT_SUBMOD_RESULT
  )

  if(NOT GIT_SUBMOD_RESULT EQUAL "0")
    message(FATAL_ERROR "git submodule update --init failed with ${GIT_SUBMOD_RESULT}")
  endif()
endif()

CMake Patterns​

Modern CMake​

Modern CMake is all about targets and properties.

Constructors of Targets:

  • add_executable()
  • add_library()

Member variables of Targets:

  • Target properties

Member functions:

  • get_target_property()
  • set_target_properties()
  • get_property(TARGET)
  • set_property(TARGET)
  • target_compile_definitions()
  • target_compile_features()
  • target_compile_options()
  • target_include_directories()
  • target_link_libraries()
  • target_sources()

Interface vs Private​

interface properties model usage requirements, whereas private properties model build requirements of targets.

Nice Patterns​

  • Think in targets (Object-Oriented)
  • Export your interface: You should be able to run from build or install
  • Write a Config.cmake file: This is what a library author should do to support clients
  • Make ALIAS targets to keep usage consistent
  • Combine common functionality into clearly documented functions
  • Use lowercase function names
  • Upper case is for variables
  • Use cmake_policy and/or range of versions

Anti Patterns​

  • Do not use global functions: e.g link_directories, include_libraries
  • Don't add unneeded PUBLIC requirements e.g -Wall
  • Don't GLOB files
  • Link to built files directly: Always link to targets if available
  • Never skip PUBLIC/PRIVATE when linking

Makefile Notes​

Makefile Macro​

foo := a.o b.o c.o
bar := $(foo:.o=.c)
first_second = Hello
a = first
b = second
all = $($a_$b)

这里的 $a_$b 组成了 first_second, 于是 $(all) 的值就是 Hello.

Built-in Makefile Macro​

  • AR: 函数库打包程序. 默认命令是 ar.
  • AS: 汇编语言编译程序. 默认命令是 as.
  • CC: C 语言编译程序. 默认命令是 cc.
  • CXX: C++语言编译程序. 默认命令是 g++.
  • CO: 从 RCS 文件中扩展文件程序. 默认命令是 co.
  • CPP: C 程序的预处理器（输出是标准输出设备）. 默认命令是 $(CC) –E.
  • FC: Fortran 和 RatFor 的编译器和预处理程序. 默认命令是 f77.
  • GET: 从 SCCS 文件中扩展文件的程序. 默认命令是 get.
  • LEX: Lex 方法分析器程序（针对于 C 或 RatFor）. 默认命令是 lex.
  • PC: Pascal 语言编译程序. 默认命令是 pc.
  • YACC: Yacc 文法分析器（针对于 C 程序）. 默认命令是 yacc.
  • YACCR: Yacc 文法分析器（针对于 RatFor 程序）. 默认命令是 yacc –r.
  • MAKEINFO: 转换 TexInfo 源文件（.texi）到 Info 文件程序. 默认命令是 makeinfo.
  • TEX: 从 TeX 源文件创建 TeX DVI 文件的程序. 默认命令是 tex.
  • TEXI2DVI: 从 TexInfo 源文件创建军 TeX DVI 文件的程序. 默认命令是 texi2dvi.
  • WEAVE: 转换 Web 到 TeX 的程序. 默认命令是 weave.
  • CWEAVE: 转换 C Web 到 TeX 的程序. 默认命令是 cweave.
  • TANGLE: 转换 Web 到 Pascal 语言的程序. 默认命令是 tangle.
  • CTANGLE: 转换 C Web 到 C. 默认命令是 ctangle.
  • RM: 删除文件命令. 默认命令是 rm –f.
  • ARFLAGS: 函数库打包程序 AR 命令的参数. 默认值是 rv.
  • ASFLAGS: 汇编语言编译器参数. （当明显地调用 .s或 .S文件时）.
  • CFLAGS: C 语言编译器参数.
  • CXXFLAGS: C++语言编译器参数.
  • COFLAGS: RCS 命令参数.
  • CPPFLAGS: C 预处理器参数. (C 和 Fortran 编译器也会用到）.
  • FFLAGS: Fortran 语言编译器参数.
  • GFLAGS: SCCS get 程序参数.
  • LDFLAGS: 链接器参数. (如: ld).
  • LFLAGS: Lex 文法分析器参数.
  • PFLAGS: Pascal 语言编译器参数.
  • RFLAGS: RatFor 程序的 Fortran 编译器参数.
  • YFLAGS: Yacc 文法分析器参数.

Built-in Makefile Variable​

  • $@: 表示规则中的目标文件集. 在模式规则中, 如果有多个目标，那么 "$@"就是匹配于目标中模式定义的集合.
  • $%: 仅当目标是函数库文件中，表示规则中的目标成员名. 例如，如果一个目标是 foo.a(bar.o)，那么 $% 就是 bar.o，$@ 就是 foo.a. 如果目标不是函数库文件 (Unix 下是[.a], Windows 下是 [.lib]), 那么其值为空.
  • $<: 依赖目标中的第一个目标名字. 如果依赖目标是以模式（即 %）定义的, 那么 $< 将是符合模式的一系列的文件集. 注意, 其是一个一个取出来的.
  • $?: 所有比目标新的依赖目标的集合. 以空格分隔.
  • $^: 所有的依赖目标的集合. 以空格分隔. 如果在依赖目标中有多个重复的，那个这个变量会去除重复的依赖目标，只保留一份.
  • $+: 这个变量很像 $^，也是所有依赖目标的集合. 只是它不去除重复的依赖目标.
  • $(@D): 表示 $@ 的目录部分 (不以斜杠作为结尾), 如果 $@ 值是 dir/foo.o，那么 $(@D) 就是 dir， 而如果 $@ 中没有包含斜杠的话，其值就是 . (当前目录).
  • $(@F): 表示 $@ 的文件部分，如果 $@ 值是 dir/foo.o, 那么 $(@F) 就是 foo.o, $(@F) 相当于函数 $(notdir $@).
  • $(*D)/$(*F): 和上面所述的同理，也是取文件的目录部分和文件部分. 对于上面的那个例子，$(*D) 返回 dir，而 $(*F) 返回 foo.
  • $(%D)/$(%F): 分别表示了函数包文件成员的目录部分和文件部分. 这对于形同 archive(member) 形式的目标中的 member 中包含了不同的目录很有用.
  • $(<D)/$(<F): 分别表示依赖文件的目录部分和文件部分.
  • $(^D)/$(^F): 分别表示所有依赖文件的目录部分和文件部分 (无相同的).
  • $(+D)/$(+F): 分别表示所有依赖文件的目录部分和文件部分 (可以有相同的).
  • $(?D)/$(?F): 分别表示被更新的依赖文件的目录部分和文件部分.

Makefile Inexplicit Rules​

Makefile C Rules​

<n>.o 的目标的依赖目标会自动推导为<n>.c, 并且其生成命令是 $(CC) –c $(CPPFLAGS) $(CFLAGS).

Makefile C++ Rules​

<n>.o 的目标的依赖目标会自动推导为 <n>.cc 或是 <n>.C, 并且其生成命令是 $(CXX) –c $(CPPFLAGS) $(CFLAGS) (建议使用 .cc 作为 C++源文件的后缀, 而不是 .C).

Makefile ASM Rules​

<n>.o 的目标的依赖目标会自动推导为<n>.s，默认使用编译品 as，并且其生成命令是： $(AS) $(ASFLAGS)。 <n>.s 的目标的依赖目标会自动推导为<n>.S，默认使用 C 预编译器 cpp，并且其生成命令是： $(AS) $(ASFLAGS)。

Makefile Object Linking​

<n>目标依赖于<n>.o，通过运行 C 的编译器来运行链接程序生成（一般是 ld），其生成命令是： $(CC) $(LDFLAGS) <n>.o $(LOADLIBES) $(LDLIBS) 这个规则对于只有一个源文件的工程有效，同时也对多个 Object 文件（由不同的源文件生成）的也有效。例如如下规则：

x : y.o z.o

并且 x.c、 y.c和 z.c都存在时，隐含规则将执行如下命令：

cc -c x.c -o x.o cc -c y.c -o y.o cc -c z.c -o z.o cc x.o y.o z.o -o x rm -f x.o rm -f y.o rm -f z.o

Makefile Function​

  • filter
  • shell
  • subst
  • wildcard

Makefile Best Practice​

$(filter %.o,$(files)): %.o: %.c
$(filter %.elc,$(files)): %.elc: %.el
$(CC) -c $(CFLAGS) $< -o $@
(%.o) : %.c
$(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $*.o
$(AR) r $@ $*.o
$(RM) $*.o
%.d: %.c
@set -e; rm -f $@; /
$(CC) -M $(CPPFLAGS) $< > $@.$$$$; /
sed 's,/($*/)/.o[ :]*,/1.o $@ : ,g' < $@.$$$$ > $@; /
$(RM) -f $@.$$$$

Reference​