Given the Makefile below,

libblah.so:  parent/a.o parent/b.o
$(CC) -shared -o $@ $^

parent/%.o: %.c | parent/ parent/child
$(CC) -c $< -o $@

parent:
mkdir -p $@
parent/child/:
mkdir -p $@

Make (v3.81, built for i486-pc-linux-gnu) successfully built the directories `parent/' and `parent/child/', the object file `parent/a.o', but failed to build `parent/b.o' with the error message:

* No rule to make target `parent/b.o', needed by `libblah.so'.  Stop.

After analyzing how make actually works, I think the problem is that make didn't recognize the `parent/' in the prereqs list of `parent/b.o' as the directory it had just built, which was actually `parent' as another target.

In my opinion, make should not make distinctions between directory names with or without trailing slashes. If all directory names are with/without the trailing slash, all will be fine (hopefully).

The patch attached below fixed this problem on my Linux box.