🚀 go-pugleaf

I'm fairly, er, gnu to DJGPP and would appreciate it if someone would
tell me what's wrong with the following makefile (whose purpose is to
build the executable file 'whoopie' from source 'whoopie.c' by compiling
and linking).  This makefile works fine when 'whoopie' or 'whoopie.o'
doesn't exist.  But if I modify 'whoopie.c', then remake, I get the
message 'whoopie is up to date' even though I can plainly see that
'whoopie.c' is newer than 'whoopie.o' and 'whoopie'.  Silly me -- I
thought that 'make' was supposed to search the entire tree of
dependencies for updated files, then act accordingly.  I've RTFM, but if
the answer's in the FM, tell me where.  Thanks for helping me grok the
almost-as-good-as-JCL syntax of makefiles!  :-}

...... TEAR ALONG PERFORATIONS ......
OBJDIR = d:/
vpath %.o $(OBJDIR)
EXEFILE = whoopie
OBJFILES = whoopie.o
           
$(EXEFILE) : $(OBJFILES)
    gcc -o $(EXEFILE) $(addprefix $(OBJDIR), $(OBJFILES)) -lm

%.o : %.c
    gcc -c -o $(OBJDIR)$@ $<
...... TEAR ALONG PERFORATIONS ......

P.S. I'm using the latest version of DJGPP (2.5.7).  My actual
makefile has tab characters before each shell command (of course, else
it wouldn't work at all).  Email responses are acceptable.
-- 
Mark A. Thomas
thommark@access.digex.net