% in makefile target match range

[password636]

Hi,

I was reading a makefile in someone else's C code. I found the percentage sign use and looked up the GNU make manual. In the manual, the sign is illustrated in a snippet as follows:

%.o: %.c
    recipe ....

The manual tells that % is a pattern matching any nonempty substring, but my question is in which range/files to match? For example, if I type `ls *' in directory /tmp, the wildcard * matches file names under /tmp. The percentage sign in makefile must have a matching range/place/files to match file names. I couldn't find the explanation in the manual. Could anyone help to explain?

Thanks a lot!

[Salem]

You have to remember that makefiles kind of work "backwards".
You start with a target, and it has dependencies to make that target.

Say for example
myprog: foo.o bar.o

Then make asks itself, OK, how do I make a foo.o?

Well for one thing, it could look for an explicit
foo.o : foo.c

But in the absence of that, it tries a matching rule instead, say
%.o : %.c
So it temporarily invents foo.o : foo.c, finds that foo.c does indeed exist, and proceeds to execute recipe to make a foo.o it can use to satisfy myprog.

[password636]

@Salem,
I got it. It's target matches against pattern rule, not pattern rule matches against target.
thank you very much!