More on VPATH

[Bgh Ello]

     Thanks for your help on my previous question, especially the comments
on automatic rules.  I'll experiment with those in due course.  For now, I
have added some include files.  hello.cpp and inc1.h are in dir1, and inc2.h
in dir2.  The makefile is now

VPATH = dir1 dir2
CC = g++
OPTS = -c -O2 -Wall
OBJS = hello.o

hello : $(OBJS)
      $(CC) -o $@ $(OBJS)

hello.o : hello.cpp inc1.h inc2.h
        $(CC) $(OPTS) $< -o $@

and the output of make is now

g++ -c -O2 -Wall dir1/hello.cpp -o hello.o
dir1/hello.cpp:6:18: fatal error: inc2.h: No such file or directory
compilation terminated.
make: *** [hello.o] Error 1

I don't understand why make doesn't find the prerequisite dir2/inc2.h.
Any help would be most appreciated.