If you do not specify any makefiles to be read with `-f' or `--file'
options, `make' will try the default makefile names; *note What Name to
Give Your Makefile: Makefile Names. Unlike makefiles explicitly
requested with `-f' or `--file' options, `make' is not certain that
these makefiles should exist. However, if a default makefile does not
exist but can be created by running `make' rules, you probably want the
rules to be run so that the makefile can be used.
Therefore, if none of the default makefiles exists, `make' will try
to make each of them in the same order in which they are searched for
(*note What Name to Give Your Makefile: Makefile Names.) until it
succeeds in making one, or it runs out of names to try. Note that it
is not an error if `make' cannot find or make any makefile; a makefile
如果你没有通过 -f 或 --file 来指定 makefile，那么 make 将会尝试缺省的 makefile名称。
(*note What Name to Give Your Makefile: Makefile Names)
如果不显式指定 -f 或 --file 选项，那么 make 是不清楚这些 makefile 是否存在的。
但是，如果一个缺省的 makefile 并不存在，但却可以通过 运行 make 规则来生成，那么你可能希望此规则得到运行以便此 makefile可以被生成和使用。
因此，如果没有缺省的makefile存在，那么make 将会试图按照它们被搜索的顺序来制作它们(*note What Name to Give Your Makefile: Makefile Names.)，知道它成功地生成了一个，或者已经试遍了所有文件。请注意如果make 不能制作或找到任何makefile，它也不是一个错误，makefile并不总是必须的。
本文转自健哥的数据花园博客园博客，原文链接：http://www.cnblogs.com/gaojian/archive/2012/09/14/2684977.html，如需转载请自行联系原作者