CMake小结2（PICO为例）

1 前言

之前写过一篇cmake，不外很简单：CMake小结_cmake ${sources}-CSDN博客
构建系统现在真的太多了，完全学不外来的感觉，meson，gardle，buildroot， Maven。。。我是真的有点放弃治疗了。之前其实CMake主打过一阵，不外那时还忙着GT的事变，所以基本上是混过来的。也没有太认真去看。
最近在看FreeRTOS，用的板子是pico，首当其冲遇到的题目就是编译环境，没想到这里用的也是CMake，前两天尝试增加了一点东西，但是报错很多。看来这次这玩意是绕不开了，结合树莓派的手册，这次就详细再看看吧。有个现实的高手的项目看，也比自己瞎学强多了。。
手册来自：https://github.com/raspberrypi/pico-sdk
详细位置是：https://rptl.io/pico-get-started

2 PICO样例工程

手册里面有一章节专门说到了怎么手动配置一个工程，Manually Create your own Project。因为是官方手册，所以说的也非常详细。

 代码如下：
test.c

1. #include <stdio.h>
2. #include "pico/stdlib.h"
3. #include "hardware/gpio.h"
4. #include "pico/binary_info.h"
6. const uint LED_PIN = 25;
8. int main()
9. {
10.         bi_decl(bi_program_description("This is a test binary."));
11.         bi_decl(bi_1pin_with_name(LED_PIN, "On-board LED"));
13.         stdio_init_all();
15.         gpio_init(LED_PIN);
16.         gpio_set_dir(LED_PIN, GPIO_OUT);
17.         while (1) {
18.                 gpio_put(LED_PIN, 0);
19.                 sleep_ms(250);
20.                 gpio_put(LED_PIN, 1);
21.                 puts("Hello World\n");
22.                 sleep_ms(1000);
23.         }
24. }

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CMakeLists.txt

1. cmake_minimum_required(VERSION 3.13)
2. include(pico_sdk_import.cmake)
4. project(test_project C CXX ASM)
6. set(CMAKE_C_STANDARD 11)
7. set(CMAKE_CXX_STANDARD 17)
9. pico_sdk_init()
10. add_executable(test test.c)
12. pico_enable_stdio_usb(test 1)
13. pico_enable_stdio_uart(test 1)
14. pico_add_extra_outputs(test)
16. target_link_libraries(test pico_stdlib)

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最后要从pico的sdk中拷贝一个文件过来。
pico_sdk_import.cmake
原始位置是在/pico-sdk/external/pico_sdk_import.cmake
此时布局如下：

创建一个build，cmake..，然后make
   对了，这里说个题外话，每次编译的时间，都说找不到picotool，所以编译工具会自己去下载，但是github在国内的稳定性大家是知道的，所以尝尝编译报错都是因为这个下不下来。所以可以先安装picotool。

1. git clone https://github.com/raspberrypi/picotool.git
2. mkdir build
3. cd build
4. cmake ..
5. make
6. make install

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cmake ..

1. tom@PC-20241221RKUQ:/mnt/e/test/pico/test/build$ cmake ..
2. Using PICO_SDK_PATH from environment ('/mnt/e/test/pico/pico-sdk')
3. PICO_SDK_PATH is /mnt/e/test/pico/pico-sdk
4. Initializing PICO_PLATFORM from environment ('rp2040')
5. Defaulting target board (PICO_BOARD) to 'pico' since not specified.
6. Using board configuration from /mnt/e/test/pico/pico-sdk/src/boards/include/boards/pico.h
7. Pico Platform (PICO_PLATFORM) is 'rp2040'.
8. -- Defaulting build type to 'Release' since not specified.
9. Defaulting compiler (PICO_COMPILER) to 'pico_arm_cortex_m0plus_gcc' since not specified.
10. Configuring toolchain based on PICO_COMPILER 'pico_arm_cortex_m0plus_gcc'
11. Defaulting PICO_GCC_TRIPLE to 'arm-none-eabi'
12. -- The C compiler identification is GNU 13.2.1
13. -- The CXX compiler identification is GNU 13.2.1
14. -- The ASM compiler identification is GNU
15. -- Found assembler: /usr/bin/arm-none-eabi-gcc
16. -- Detecting C compiler ABI info
17. -- Detecting C compiler ABI info - done
18. -- Check for working C compiler: /usr/bin/arm-none-eabi-gcc - skipped
19. -- Detecting C compile features
20. -- Detecting C compile features - done
21. -- Detecting CXX compiler ABI info
22. -- Detecting CXX compiler ABI info - done
23. -- Check for working CXX compiler: /usr/bin/arm-none-eabi-g++ - skipped
24. -- Detecting CXX compile features
25. -- Detecting CXX compile features - done
26. Build type is Release
27. -- Found Python3: /usr/bin/python3 (found version "3.12.3") found components: Interpreter
28. TinyUSB available at /mnt/e/test/pico/pico-sdk/lib/tinyusb/src/portable/raspberrypi/rp2040; enabling build support for USB.
29. BTstack available at /mnt/e/test/pico/pico-sdk/lib/btstack
30. cyw43-driver available at /mnt/e/test/pico/pico-sdk/lib/cyw43-driver
31. lwIP available at /mnt/e/test/pico/pico-sdk/lib/lwip
32. mbedtls available at /mnt/e/test/pico/pico-sdk/lib/mbedtls
33. -- Configuring done (7.6s)
34. -- Generating done (6.3s)
35. -- Build files have been written to: /mnt/e/test/pico/test/build

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make

1. tom@PC-20241221RKUQ:/mnt/e/test/pico/test/build$ make
2. [  1%] Building ASM object pico-sdk/src/rp2040/boot_stage2/CMakeFiles/bs2_default.dir/compile_time_choice.S.o
3. [  2%] Linking ASM executable bs2_default.elf
4. [  2%] Built target bs2_default
5. [  3%] Generating bs2_default.bin
6. [  4%] Generating bs2_default_padded_checksummed.S
7. [  5%] Building ASM object pico-sdk/src/rp2040/boot_stage2/CMakeFiles/bs2_default_library.dir/bs2_default_padded_checksummed.S.o
8. [  5%] Built target bs2_default_library
9. make[2]: Warning: File 'CMakeFiles/test.dir/depend.make' has modification time 0.5 s in the future
10. [  6%] Building C object CMakeFiles/test.dir/test.c.o
11. [  7%] Building C object CMakeFiles/test.dir/mnt/e/test/pico/pico-sdk/src/rp2_common/pico_stdlib/stdlib.c.o
12. [  9%] Building C object CMakeFiles/test.dir/mnt/e/test/pico/pico-sdk/src/rp2_common/hardware_gpio/gpio.c.o
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92. [100%] Linking CXX executable test.elf
93. make[2]: warning:  Clock skew detected.  Your build may be incomplete.
94. [100%] Built target test

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好了，看来这个cmake里面干的事变还不少。

3 再看CMake

 CMake的基本原理这里就不多说了，其实就是一个构建脚本的再抽象。

官网上有一个详细的教程：
https://cmake.org/cmake/help/latest/_downloads/feee7c51d38ca0ca2395c3e89ac3d30e/cmake-4.0.0-rc2-tutorial-source.zip
CMake Tutorial — CMake 4.0.0-rc2 Documentation
他家另有一个网课，不外现在貌似是关闭了。
CMake Training

对于CMake的重点是谁人CMakeLists.txt，下面列了我以为最常用几个，完了命令行再看看大体也差不多了。

名称	作用
cmake_minimum_required(VERSION <min_version>)	指定项目所需的最低 CMake 版本
project(<project_name> [LANGUAGES <language>...])	定义项目名称和使用的编程语言
add_executable(<target_name> <source_files>...)	添加一个可实行文件目标，并指定其源文件
add_library(<target_name> [STATIC | SHARED | MODULE] <source_files>...)	添加一个库目标，可以是静态库、动态库或模块库
target_link_libraries(<target_name> <libraries>...)	指定目标须要链接的库
include_directories(<dir>...)	添加头文件搜刮路径
target_include_directories(<target_name> <INTERFACE|PUBLIC|PRIVATE> <dir>...)	为特定目标添加头文件搜刮路径
add_subdirectory(<source_dir> [binary_dir])	添加子目次，子目次必须包含CMakeLists.txt 文件
set(<variable> <value> [CACHE <type> <docstring> [FORCE]])	设置变量的值
add_definitions(<definitions>...)	添加预处置处罚器定义
add_custom_target(<target_name> [ALL] [command]...)	添加一个自定义目标，通常用于实行自定义命令
message([<mode>] "message text")	打印消息，用于调试或信息输出

详细的命令阐明可以看：cmake-commands(7) — CMake 4.0.0-rc2 Documentation
另有很多内置变量须要相识一下：
PROJECT_NAME：当前项目的名称，由 project() 命令设置。
PROJECT_SOURCE_DIR：当前项目的根目次（包含顶级 CMakeLists.txt 的目次）。
PROJECT_BINARY_DIR：当前项目的构建目次（通常是 build 目次）。
CMAKE_SOURCE_DIR：顶级 CMakeLists.txt 所在的目次（与 PROJECT_SOURCE_DIR 雷同）。
CMAKE_BINARY_DIR：顶级构建目次（与 PROJECT_BINARY_DIR 雷同）。
CMAKE_CURRENT_SOURCE_DIR：当前正在处置处罚的 CMakeLists.txt 文件所在的目次。
CMAKE_CURRENT_BINARY_DIR：当前正在处置处罚的 CMakeLists.txt 文件对应的构建目次。
CMAKE_CURRENT_LIST_DIR：当前正在处置处罚的 CMake 脚本文件（如 CMakeLists.txt 或 .cmake 文件）所在的目次。
此外，CMake 还可以通过 $ENV{VAR_NAME} 访问系统的环境变量


4 PICO样例工程分析

因为这次的重心不是代码，所以这里代码就不看了。
重点照旧CMakeLists.txt，这次一行一行的过。

1. cmake_minimum_required(VERSION 3.13)
2. include(pico_sdk_import.cmake)
4. project(test_project C CXX ASM)
6. set(CMAKE_C_STANDARD 11)
7. set(CMAKE_CXX_STANDARD 17)
9. pico_sdk_init()
10. add_executable(test test.c)
12. pico_enable_stdio_usb(test 1)
13. pico_enable_stdio_uart(test 1)
14. pico_add_extra_outputs(test)
16. target_link_libraries(test pico_stdlib)

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从列表来看，PICO是自己扩展了不少函数，重点要看的就是include(pico_sdk_import.cmake)，pico_sdk_init()，pico_add_extra_outputs(test)。至于pico_enable_stdio_usb(test 1)，pico_enable_stdio_uart(test 1)感觉就是两个宏定义。

include(pico_sdk_import.cmake)
这个主要是配置pico的路径，如果没有配置PICO_SDK_PATH，会直接从github去下载。真正的初始化，是后面include pico_sdk_init.cmake。在这里，就定义了这个宏ico_sdk_init()。

1.     macro(pico_sdk_init)
2.         if (NOT CMAKE_PROJECT_NAME)
3.             message(WARNING "pico_sdk_init() should be called after the project is created (and languages added)")
4.         endif()
5.         add_subdirectory(${PICO_SDK_PATH} pico-sdk)
6.     endmacro()

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这里就是包含了pico-sdk里面的第一个CMakeLists.txt。和我们一般使用库差别，一般就是只要头文件，然后静态或者动态链接。这里是相当于你编译一个小程序，现实上也是把整个pico-sdk加进来了的。

至于pico_add_extra_outputs(test)。
这个的定义是在：pico-sdk/src/cmake/on_device.cmake，这个是一个function定义，不是之前的macro。

1. function(pico_add_extra_outputs TARGET)
2.     # Disassembly will be nonsense for encrypted binaries,
3.     # so disassemble before picotool processing
4.     pico_add_dis_output(${TARGET})
6.     # Picotool processing (signing/encrypting/etc)
7.     # PICO_CMAKE_CONFIG: PICO_NO_PICOTOOL, Disable use/requirement for picotool meaning that UF2 output and signing/hashing and coprocoessor disassembly will all be unavailable, type=bool, default=0, group=build
8.     if (NOT PICO_NO_PICOTOOL)
9.         picotool_postprocess_binary(${TARGET} IS_ENCRYPTED)
10.     endif()
12.     if (PICO_32BIT)
13.         pico_add_hex_output(${TARGET})
14.     endif()
15.     pico_add_bin_output(${TARGET})
16.     pico_add_map_output(${TARGET})
18.     # PICO_CMAKE_CONFIG: PICO_NO_TARGET_NAME, Don't define PICO_TARGET_NAME, type=bool, default=0, group=build
19.     # PICO_BUILD_DEFINE: PICO_TARGET_NAME, Name of the build target being compiled (unless PICO_NO_TARGET_NAME set in build), type=string, default=target name, group=build
20.     if (NOT PICO_NO_TARGET_NAME)
21.         target_compile_definitions(${TARGET} PRIVATE
22.                 PICO_TARGET_NAME="${TARGET}"
23.                 )
24.     endif()
26.     if (PICO_SYMLINK_ELF_AS_FILENAME)
27.         add_custom_target(${TARGET}_symlinked)
28.         add_dependencies(${TARGET}_symlinked ${TARGET})
30.         add_custom_command(TARGET ${TARGET}_symlinked POST_BUILD
31.                 COMMAND rm -f "${PICO_SYMLINK_ELF_AS_FILENAME}"
32.                 COMMAND ln -s -r $<TARGET_FILE:${TARGET}> "${PICO_SYMLINK_ELF_AS_FILENAME}"
33.                 COMMENT "Symlinking from ${PICO_SYMLINK_ELF_AS_FILENAME} to ${TARGET}"
34.                 )
35.     endif ()
36.     # PICO_CMAKE_CONFIG: PICO_NO_UF2, Disable UF2 output, type=bool, default=0, group=build
37.     if (NOT (PICO_NO_UF2 OR PICO_NO_PICOTOOL))
38.         pico_add_uf2_output(${TARGET})
39.     endif()
40. endfunction()

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这里还包含了很多个其它的函数，大体就是将编译的程序最后转换成可以在板子上运行的uf2格式。

5 增加FreeRTOS支持

回到之前的那一篇：RTOS基础1（FreeRTOS+树莓派PICO环境）-CSDN博客
看看里面加了什么。

 增加了自己的一个freertos，另有一个pico_sdk_import.cmake。
它的CMakeLists.txt是如许的

1. cmake_minimum_required(VERSION 3.12)
3. include(pico_sdk_import.cmake)
5. project(Pico-FreeRTOS)
7. pico_sdk_init()
9. add_subdirectory(freertos)
10. add_subdirectory(ProjectFiles)

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多出来的一句就是add_subdirectory(freertos)
再看看子CMakeLists.txt，也就是ProjectFiles里面的。

1. add_executable(blink main.c)
3. pico_sdk_init()
5. target_link_libraries(blink pico_stdlib freertos)
6. pico_add_extra_outputs(blink)

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其实就是一个，target_link_libraries(blink pico_stdlib freertos)，增加链接freertos的库就可以了。
好吧，好像确实也不难哈。明天再继承试试。。。

6 小结

CMake的东西确实比我想的要多多了。
个人以为，现实上它有两个很大的作用。
1 就是跨平台的构建。比如说一套编译脚本，可以在linux，苹果，windows下都搞定了。这个之前都知道。
2  针对自动化构建，做了很多内容。比如创建宏或者函数，处置处罚github下载这些，这些从前的makefile确实解决这些不那么方便。这部门CMake险些是增加了半套语言。。。当然，如果能换成python语言就更好了。

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