automake.ac 和automake.in的区别.

老版本autoconf支持automake.in,不过现在尽量首选使用automake.ac.

官方文档给出介绍Previous versions of Autoconf promoted the name configure.in, which is somewhat ambiguous (the tool needed to process this file is not described by its extension), and introduces a slight confusion with config.h.in and so on (for which ‘.in’ means “to be processed by configure”). Using configure.ac is now preferred.

意思就是,如果用automake.in 容易和autoheader 产生的config.h.in产生扩展名冲突,因为.in文件是configure要处理的文件.

不过如果用automake.in  会出现警告:

me@me:~/Desktop/littlefunction/automake_library$ aclocal
aclocal: warning: autoconf input should be named 'configure.ac', not 'configure.in'