🚀 go-pugleaf

I've only recently started using GNU make, and I'm having a problem 
with the default archiving rules.


E.g. Say the Makefile is:

libfoo.a: libfoo.a(file.o)
	ranlib libfoo.a

And there is a source file named file.c.  Then

>make
cc    -c file.c -o file.o
ar rv libfoo.a file.o
a - file.o
ar: creating libfoo.a
ranlib libfoo.a
rm  file.o                         # Everything ok so far
>make
ar rv libfoo.a file.o              # Why does it do this????
ar: cannot open file.o
>

The second time it shouldn't do anything (except maybe say "`libfoo.a' is up 
to date"), since file.c has not been modified.  It looks like the (built-in)
chained dependency is not being handled properly.

I tried adding an implicit rule that would skip the chaining (.o) -> .o -> .c,
instead going directly (.o) -> .c :

(%.o): %.c
	$(COMPILE.c) -o $% $<
	$(AR) $(ARFLAGS) $@ $%
	$(RM) $%


With this implicit rule added, the object is archived properly.

But this extra rule shouldn't be necessary, should it?
Can anyone explain this?

Thanks,
Ray