進階使用CMake編譯程式碼

一則故事

寫程式一般透過gcc或g++等編譯器 (Compiler)，將程式碼 (Code) 轉為可執行檔 (Program)
隨著系統越加龐大，程式碼檔案數量也隨之增加，程式碼間的關聯性錯綜複雜，為了處理複雜的程式碼編譯，並降低開發與維護程式碼的困難度，make工具便被開發出來。make工具算是批次處理工具，它參照makefile內的規則與相依性，依次編譯程式碼，直到最終目標文件被生成。而這個makefile並非憑空出生，它仍然需要被工程師們撰寫出來。
然而，編寫一個makefile有時十分麻煩，尤其在一個複雜系統內。或者，在更換目標平台時，makefile內的編譯器或路徑等資訊也需要被修改。因此，cmake工具就被開發出來，這是一個能夠自動化生成各式makefile的工具，它根據CMakeList.txt內的規則、函式庫關聯生成適用於目標平台的makefile。當然，CMakeList.txt也非憑空而來，它仍然需要被工程師們撰寫出來。

以Ne10為範例認識cmake跟cmakelists.txt

只要透過cmake與make就能完成Ne10的編譯，Ne10的交叉編譯筆記可以參考這裡。

這裡節錄一些Ne10開頭的cmakelists.txt：

cmake_minimum_required(VERSION 2.6)

project(NE10 C CXX ASM)

option(NE10_BUILD_SHARED "Build NE10 shared libraries" OFF)
option(NE10_BUILD_STATIC "Build NE10 static libraries" ON)
option(NE10_BUILD_EXAMPLES "Build NE10 examples" ON)

#hard float abi
option(NE10_ARM_HARD_FLOAT "Build NE10 for hard float abi" ON)

#unit test options
option(NE10_BUILD_UNIT_TEST "Build NE10 unit test" OFF)

......(省略)......

# Add NE10 library sub-directory.
add_subdirectory(modules)

if(NE10_BUILD_EXAMPLES AND NE10_ENABLE_MATH)
    add_subdirectory(samples)
endif()

if(NE10_BUILD_UNIT_TEST)
    add_subdirectory(test)
endif()

......(省略)......

Ne10的子資料夾下還有其他關聯的cmakelists.txt，例如modules/CMakeLists.txt：

......(省略)......

if(NE10_ENABLE_MATH)
    #enable NE10_init_math
    add_definitions(-DNE10_ENABLE_MATH)
    # Add math C files.
    set(NE10_MATH_C_SRCS
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_abs.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_addc.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_add.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_divc.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_div.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_len.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_mlac.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_mla.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_mulc.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_mul.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_normalize.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_rsbc.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_setc.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_subc.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_sub.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_dot.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_cross.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_addmat.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_submat.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_mulmat.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_mulcmatvec.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_detmat.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_invmat.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_transmat.c
        ${PROJECT_SOURCE_DIR}/modules/math/NE10_identitymat.c
    )

......(省略)......

if(NE10_BUILD_SHARED)

    add_library( NE10_shared SHARED
        ${NE10_C_SRCS}
        ${NE10_INTRINSIC_SRCS}
        ${NE10_NEON_SRCS}
        ${NE10_INIT_SRCS}
    )

    target_link_libraries(NE10_shared m)

    set_target_properties(NE10_shared PROPERTIES
        OUTPUT_NAME "NE10"
        CLEAN_DIRECT_OUTPUT 1
        VERSION ${NE10_VERSION}
        LINKER_LANGUAGE C
    )

    add_library( NE10_test SHARED
        ${NE10_C_SRCS}
        ${NE10_INTRINSIC_SRCS}
        ${NE10_NEON_SRCS}
        ${NE10_INIT_SRCS}
    )

    set_target_properties(NE10_test PROPERTIES
        OUTPUT_NAME "NE10_test"
        CLEAN_DIRECT_OUTPUT 1
        VERSION ${NE10_VERSION}
    )

    target_link_libraries(NE10_test m)

endif()

另外，Ne10裡面還有一個檔案GNUlinux_config.cmake，這是cmake預留的接口，只要cmake時透過CMAKE_TOOLCHAIN_FILE指定.cmake結尾的設定檔，就能方便置換交叉編譯的工具鏈 (toolchain)。下面是N10的GNUlinux_config.cmake節錄：

set(GNULINUX_PLATFORM ON)
set(CMAKE_SYSTEM_NAME "Linux")
set(CMAKE_SYSTEM_PROCESSOR "arm")

if(NOT DEFINED ENV{NE10_LINUX_TARGET_ARCH})
   set(NE10_LINUX_TARGET_ARCH "armv7")
else()
   set(NE10_LINUX_TARGET_ARCH $ENV{NE10_LINUX_TARGET_ARCH})
endif()

if(NE10_LINUX_TARGET_ARCH STREQUAL "armv7")
   set(CMAKE_C_COMPILER arm-linux-gnueabihf-gcc)
   set(CMAKE_CXX_COMPILER arm-linux-gnueabihf-g++)
   set(CMAKE_ASM_COMPILER arm-linux-gnueabihf-as)
   find_program(CMAKE_AR NAMES "arm-linux-gnueabihf-ar")
   find_program(CMAKE_RANLIB NAMES "arm-linux-gnueabihf-ranlib")
elseif(NE10_LINUX_TARGET_ARCH STREQUAL "aarch64")
   set(CMAKE_C_COMPILER aarch64-linux-gnu-gcc)
   set(CMAKE_CXX_COMPILER aarch64-linux-gnu-g++)
   set(CMAKE_ASM_COMPILER aarch64-linux-gnu-as)
   find_program(CMAKE_AR NAMES "aarch64-linux-gnu-ar")
   find_program(CMAKE_RANLIB NAMES "aarch64-linux-gnu-ranlib")
endif()

mark_as_advanced(CMAKE_AR)
mark_as_advanced(CMAKE_RANLIB)

進階使用CMake編譯程式碼

Note of Using CMake for Compilation in Advance

目錄

一則故事

以Ne10為範例認識cmake跟cmakelists.txt

Reference