[vox-tech] makefile question - auto dependencies

[Peter Jay Salzman]

begin Mike Simons <msimons@moria.simons-clan.com> 
> On Fri, Mar 21, 2003 at 10:18:21AM -0800, Peter Jay Salzman wrote:
> > i was playing around with auto-dependencies with makefiles the other
> > day.  here's a hello world example of the technique:
> > 
> 
> >    OBJS   = $(patsubst %.c, %.o, $(wildcard *.c))
> >    SRCS   = $(wildcard *.c)
> 
> should use SRCS in OBJS list.

aha.  yes, thanks!

> >    DEPDIR = .deps
> >    vpath %.d ${DEPDIR}
> 
> I don't use vpath in the sample above... can add if you want.
> 
> > into a single line saying that all .o files depend on the corresponding
> > .d file?
> 
>   I used to use a nasty sed expression to make the .d files, but for
> some reason decided that they were not needed.
> 
>   The .o's do not depend on the .d.
> 
>   Both the .d and .o the depend on the .c.
 
yes again.  :)   and user supplied .h files as well.

>   Here is a current sample of Makefile which I use to build programs
> with, stripped down to only work on C code... below no user servicable
> parts is the stuff that does auto building.
>   Rules are written for C++, ProC, LaTeX, etc.
> 
>   If you only want a single target to make life simplier you can replace 
> go,s2,s3 with:
> ===
> ${TARGET}: ${OFILES}
> 	gcc ${CFLAGS} -o $@ $^ ${LFLAGS}
> ===
> 
>   If you care to use a special LD variable to id the linker
> stuff ...
> 
> ====
> TARGET := go
> 
> CC := gcc
> CFLAGS := -g -Wall -W -O9
> CFLAGS := -g -Wall -W
> LFLAGS := -lm
> 
> all: ${TARGET}
> 
> go: main.o
> 	gcc ${CFLAGS} -o $@ $^ ${LFLAGS}
> s2: s2.o
> 	gcc ${CFLAGS} -o $@ $^ ${LFLAGS}
> s3: s3.o
> 	gcc ${CFLAGS} -o $@ $^ ${LFLAGS}
> 
> ################
> # no user servicable parts below here... so don't change below here
> ################
> %.o: %.c
> 	gcc ${CFLAGS} -c $^
> 
> .%.d: %.c
> 	@gcc -MM ${CFLAGS} -o $@ $^
> 
> clean:
> 	rm -rf *.o
> 
> nuke: clean
> 	rm -rf ${DFILES} $(TARGET)
> 
> CFILES := ${wildcard *.c}
> OFILES := ${patsubst %.c,%.o,${CFILES}}
> DFILES := ${patsubst %.c,.%.d,${CFILES}}
> 
> ifneq ($(MAKECMDGOALS),nuke)
> -include ${DFILES}
> endif

hi mike,

i figured you'd answer.   ;)

if i'm not mistaken, you're ignoring the dependencies of the .d files on
the .c and .h files.  in other words, your .d file will look like:

   main.o : main.c main.h

when it should look like:

   main.o main.d : main.c main.h

that's what the awful sed script does (i think).


also, is the .o->.c explicit rule really necessary?  make already knows
how to make .o files from .c files.

pete

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