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。

your source files --> [autoscan*] --> [configure.scan] --> configure.ac

user input files   optional input     process          output files
================   ==============     =======          ============
                    acinclude.m4 - - - - -.
                                      .-------,
configure.ac ------------------------>|aclocal|
                 {user macro files} ->|       |------> aclocal.m4
                                      `-------'
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
user input files    optional input     process          output files
================    ==============     =======          ============
                    aclocal.m4 - - - - - - - .
                                     .----------,
configure.ac ----------------------->|autoheader|----> autoconfig.h.in
                                     `----------'

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

user input files   optional input   processes          output files
================   ==============   =========          ============
                                     .--------,
                                     |        | - - -> COPYING
                                     |        | - - -> INSTALL
                                     |        |------> install-sh
                                     |        |------> missing
                                     |automake|------> mkinstalldirs
configure.ac ----------------------->|        |
Makefile.am  ----------------------->|        |------> Makefile.in
                                     |        |------> stamp-h.in
                                 .---+        | - - -> config.guess
                                 |   |        | - - -> config.sub
                                 |   `------+-'
                                 |          | - - - -> config.guess
                                 |libtoolize| - - - -> config.sub
                                 |          |--------> ltmain.sh
                                 |          |--------> ltconfig
                                 `----------'

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。

user input files   optional input   processes          output files
================   ==============   =========          ============
aclocal.m4 ,autoconfig.h.in - - - - - - -.
                                     .--------,
configure.ac ----------------------->|autoconf|------> configure

6. ./configure的过程

                                           .-------------> [config.cache]
     configure* --------------------------+-------------> config.log
              [config.h.in] -.            v            .--> [autoconfig.h]
                             +-------> config.status* -+                   
              Makefile.in ---'                         `-->   Makefile

7. make过程

     [autoconfig.h] -.
                     +--> make* --->  程序
       Makefile   ---'

                                     .---------,
                   config.site - - ->|         |
                  config.cache - - ->|         | - - -> config.cache
                                     |         +-,
                                     `-+-------' |
                                       |         |----> config.status
                   config.h.in ------->|config-  |----> config.h
                   Makefile.in ------->|  .status|----> Makefile
                                       |         |----> stamp-h
                                       |         +--,
                                     .-+         |  |
                                     | `------+--'  |
                   ltmain.sh ------->|ltconfig|-------> libtool
                                     |        |     |
                                     `-+------'     |
                                       |config.guess|
                                       | config.sub |
                                       `------------'
 
                                   .--------,
                   Makefile ------>|        |
                   config.h ------>|        |
{project sources} ---------------->|        |--------> {project targets}
                                 .-+        +--,
                                 | `--------'  |
                                 |   libtool   |
                                 |   missing   |
                                 |  install-sh |
                                 |mkinstalldirs|
                                 `-------------'