【RT-Thread学习笔记】使用scons命令生成静态库

1 问题来源

本问题来源于RT-Thread的技术论坛的一个常见问题，当时我回答了这个问题，很荣幸拿了一个最佳答案，为了能够再次消化并进行知识点沉淀，我把这个问题再次抛到这里。 原问题，请戳这里：scons 命令buildlib使用方法

2 实践分析

2.1 不懂就要问

既然不知道怎么用scons，那么我们先看到它的帮助信息，以下命令在scons的主目录执行，即可以找到Sconscript的目录下执行：

1. rt-thread/bsp/qemu-vexpress-a9$ scons -h
2. scons: Reading SConscript files ...
3. drivers/SConscript
4. applications/SConscript
5. [, , ]
6. scons: done reading SConscript files.
7. usage: scons [OPTION] [TARGET] ...
9. SCons Options:
10. -b, -d, -e, -m, -S, -t, -w, --environment-overrides, --no-keep-going,
11. --no-print-directory, --print-directory, --stop, --touch
12. Ignored for compatibility.
13. -c, --clean, --remove Remove specified targets and dependencies.
14. -C DIR, --directory=DIR Change to DIR before doing anything.
15. --cache-debug=FILE Print CacheDir debug info to FILE.
16. --cache-disable, --no-cache
17. Do not retrieve built targets from CacheDir.
18. --cache-force, --cache-populate
19. Copy already-built targets into the CacheDir.
20. --cache-readonly Do not update CacheDir with built targets.
21. --cache-show Print build actions for files from CacheDir.
22. --config=MODE Controls Configure subsystem: auto, force,
23. cache.
24. -D Search up directory tree for SConstruct,
25. build all Default() targets.
26. --debug=TYPE Print various types of debugging information:
27. count, duplicate, explain, findlibs, includes,
28. memoizer, memory, objects, pdb, prepare,
29. presub, stacktrace, time, action-timestamps.
30. --diskcheck=TYPE Enable specific on-disk checks.
31. --duplicate=DUPLICATE Set the preferred duplication methods. Must be
32. one of hard-soft-copy, soft-hard-copy,
33. hard-copy, soft-copy, copy
34. --enable-virtualenv Import certain virtualenv variables to SCons
35. -f FILE, --file=FILE, --makefile=FILE, --sconstruct=FILE
36. Read FILE as the top-level SConstruct file.
37. -h, --help Print defined help message, or this one.
38. -H, --help-options Print this message and exit.
39. -i, --ignore-errors Ignore errors from build actions.
40. -I DIR, --include-dir=DIR Search DIR for imported Python modules.
41. --ignore-virtualenv Do not import virtualenv variables to SCons
42. --implicit-cache Cache implicit dependencies
43. --implicit-deps-changed Ignore cached implicit dependencies.
44. --implicit-deps-unchanged Ignore changes in implicit dependencies.
45. --interact, --interactive Run in interactive mode.
46. -j N, --jobs=N Allow N jobs at once.
47. -k, --keep-going Keep going when a target can't be made.
48. --max-drift=N Set maximum system clock drift to N seconds.
49. --md5-chunksize=N Set chunk-size for MD5 signature computation to
50. N kilobytes.
51. -n, --no-exec, --just-print, --dry-run, --recon
52. Don't build; just print commands.
53. --no-site-dir Don't search or use the usual site_scons dir.
54. --profile=FILE Profile SCons and put results in FILE.
55. -q, --question Don't build; exit status says if up to date.
56. -Q Suppress "Reading/Building" progress messages.
57. --random Build dependencies in random order.
58. -s, --silent, --quiet Don't print commands.
59. --site-dir=DIR Use DIR instead of the usual site_scons dir.
60. --stack-size=N Set the stack size of the threads used to run
61. jobs to N kilobytes.
62. --taskmastertrace=FILE Trace Node evaluation to FILE.
63. --tree=OPTIONS Print a dependency tree in various formats: all,
64. derived, prune, status, linedraw.
65. -u, --up, --search-up Search up directory tree for SConstruct,
66. build targets at or below current directory.
67. -U Search up directory tree for SConstruct,
68. build Default() targets from local SConscript.
69. -v, --version Print the SCons version number and exit.
70. --warn=WARNING-SPEC, --warning=WARNING-SPEC
71. Enable or disable warnings.
72. -Y REPOSITORY, --repository=REPOSITORY, --srcdir=REPOSITORY
73. Search REPOSITORY for source and target files.
75. Local Options:
76. --dist make distribution
77. --dist-strip make distribution and strip useless files
78. --dist-ide make distribution for RT-Thread Studio IDE
79. --project-path=PROJECT-PATH
80. set dist-ide project output path
81. --project-name=PROJECT-NAME
82. set project name
83. --reset-project-config reset the project configurations to default
84. --cscope Build Cscope cross reference database. Requires
85. cscope installed.
86. --clang-analyzer Perform static analyze with Clang-analyzer.
87. Requires Clang installed. It is recommended to
88. use with scan-build like this: `scan-build
89. scons --clang-analyzer` If things goes well,
90. scan-build will instruct you to invoke
91. scan-view.
92. --buildlib=BUILDLIB building library of a component
93. --cleanlib clean up the library by --buildlib
94. --target=TARGET set target project: mdk/mdk4/mdk5/iar/vs/vsc/ua/
95. cdk/ses/makefile/eclipse/codelite/cmake
96. --stackanalysis thread stack static analysis
97. --genconfig Generate .config from rtconfig.h
98. --useconfig=USECONFIG make rtconfig.h from config file.
99. --verbose print verbose information during build
100. --menuconfig make menuconfig for RT-Thread BSP
101. --pyconfig Python GUI menuconfig for RT-Thread BSP
102. --pyconfig-silent Don`t show pyconfig window

精准匹配下：

1. rt-thread/bsp/qemu-vexpress-a9$ scons -h | grep buildlib
2. --buildlib=BUILDLIB building library of a component
3. --cleanlib clean up the library by --buildlib

2.2 实践出整理

从上面的帮助信息，我们已经找到关键信息了，我们来实践下：

1. rt-thread/bsp/qemu-vexpress-a9$ scons --buildlib=BUILDLIB
2. scons: Reading SConscript files ...
3. b''
4. drivers/SConscript
5. applications/SConscript
6. [, , ]
7. scons: done reading SConscript files.
8. scons: Building targets ...
9. scons: building associated VariantDir targets: build
10. scons: `.' is up to date.
11. scons: done building targets.

发现并没有生成，仔细一看，这个buildlib=后面跟的名称不是乱填的，是需要填写你当前目录下，已经使用scons语法配置好的组件，这个东西在scons里面是叫Group。 通俗来说，就是使用buildlib，一个Gourp就可以生成一个库。 我们再来实践下，以bsp/qemu-vexpress-a9的Application这个Group为例，在其applications目录有定义Sconsript:

那么就可以输入scons--buildlib=Applications

就可以将Applications那个group定义的C文件编译打包成一个静态库，输出也是位于bsp的目录中。

3 经验总结

• 任何命令行指令，千万不要放过它的help信息
• scons 使用--buildlib=xxx轻松生存库文件，库名称为libxxx.a

4 更多分享

架构师李肯

一个专注于嵌入式IoT领域的架构师。有着近10年的嵌入式一线开发经验，深耕IoT领域多年，熟知IoT领域的业务发展，深度掌握IoT领域的相关技术栈，包括但不限于主流RTOS内核的实现及其移植、硬件驱动移植开发、网络通讯协议开发、编译构建原理及其实现、底层汇编及编译原理、编译优化及代码重构、主流IoT云平台的对接、嵌入式IoT系统的架构设计等等。拥有多项IoT领域的发明专利，热衷于技术分享，有多年撰写技术博客的经验积累，连续多月获得RT-Thread官方技术社区原创技术博文优秀奖，荣获CSDN博客专家、CSDN物联网领域优质创作者、2021年度CSDN&RT-Thread技术社区之星、RT-Thread官方嵌入式开源社区认证专家、RT-Thread 2021年度论坛之星TOP4、华为云云享专家（嵌入式物联网架构设计师）等荣誉。坚信【知识改变命运，技术改变世界】！

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