图解aclocal、autoconf、automake、autoheader、configure

1. 1.autoscan (autoconf): 扫描源代码以搜寻普通的可移植性问题，比如检查编译器，库，头文件等，生成文件configure.scan,它是configure.ac的一个雏形。
2. 2.aclocal (automake):根据已经安装的宏，用户定义宏和acinclude.m4文件中的宏将configure.ac文件所需要的宏集中定义到文件 aclocal.m4中。aclocal是一个perl 脚本程序，它的定义是：“aclocal - create aclocal.m4 by scanning configure.ac”
3.  
4. user input files   optional input      process        output files
5. ================   ==============      =======        ============
6.  
7.                     acinclude.m4 - - - - -.
8.                                           V
9.                                       .-------,
10. configure.ac ------------------------>|aclocal|
11.                  {user macro files} ->|       |------> aclocal.m4
12.                                       `-------'
13. 3.autoheader(autoconf): 根据configure.ac中的某些宏，比如cpp宏定义，运行m4，声称config.h.in
14.  
15. user input files    optional input      process        output files
16. ================    ==============      =======         ============
17.  
18.                     aclocal.m4 - - - - - - - .
19.                                              |
20.                                              V
21.                                      .----------,
22. configure.ac ----------------------->|autoheader|----> autoconfig.h.in
23.                                      `----------'
24. 4.automake: automake将Makefile.am中定义的结构建立Makefile.in，然后configure脚本将生成的Makefile.in文件转换为Makefile。如果在configure.ac中定义了一些特殊的宏，比如AC_PROG_LIBTOOL，它会调用libtoolize，否则它会自己产生config.guess和config.sub
25.  
26. user input files optional input     processes          output files
27. ================ ==============     =========          ============
28.  
29.                                      .--------,
30.                                      |        | - - -> COPYING
31.                                      |        | - - -> INSTALL
32.                                      |        |------> install-sh
33.                                      |        |------> missing
34.                                      |automake|------> mkinstalldirs
35. configure.ac ----------------------->|        |
36. Makefile.am  ----------------------->|        |------> Makefile.in
37.                                      |        |------> stamp-h.in
38.                                  .---+        | - - -> config.guess
39.                                  |   |        | - - -> config.sub
40.                                  |   `------+-'
41.                                  |          | - - - -> config.guess
42.                                  |libtoolize| - - - -> config.sub
43.                                  |          |--------> ltmain.sh
44.                                  |          |--------> ltconfig
45.                                  `----------'
46. 5.autoconf:将configure.ac中的宏展开，生成configure脚本。这个过程可能要用到aclocal.m4中定义的宏。
47.  
48. user input files    optional input   processes       output files
49. ================    ==============   =========       ============
50.  
51.                    aclocal.m4 - - - - - -.
52.                                          V
53.                                      .--------,
54. configure.ac ----------------------->|autoconf|------> configure ----->autoconfig.h,Makefile