how does make know that 'nothing to be done for \'all\''

Thinking · 07-06-2006, 09:40 AM

hiho@ll

i'm just wondering how the program "make" knows when the files have changed and recompilation is needed?

the background of this question is, that i have wrote my own makefile
and from other makefiles (other projects) i know the message "nothing to be done for ..."
but my makefile recompiles everything everytime i call it

what i want:
>make all
# some compilation stuff
>make all
nothing to be done for all

what i get:
>make all
# some compilation stuff
>make all
# some compilation stuff

the makefile looks like this:

Code:

OWNER=username
GROUP=groupname
CFLAGS= -g -g3 -ggdb -ggdb3 -O4 -ldl -rdynamic -Wl,-export-dynamic -Wall
CLIBFLAGS= -g -g3 -ggdb -ggdb3 -O4 -fPIC -Wall -Wl,-export-dynamic -shared
CCOMP= -g -g3 -ggdb -ggdb3 -O4 -Wall -fPIC
SRCS=utils/classone.cpp utils/classtwo.cpp daemon.cpp server.cpp
OBJS=utils/classone.o utils/classtwo.o daemon.o server.o
INCLUDES= -Iutils
CC=g++
BINDIR=/usr/local/project

all: objects partone parttwo

objects:
    $(CC) $(CCOMP) $(INCLUDES) -c utils/classone.cpp -o utils/classone.o
    $(CC) $(CCOMP) $(INCLUDES) -c utils/classtwo.cpp -o utils/classtwo.o
    $(CC) $(CCOMP) $(INCLUDES) -c daemon.cpp -o daemon.o
    $(CC) $(CCOMP) $(INCLUDES) -c server.cpp -o server.o

partone:
    $(CC) $(CFLAGS) $(INCLUDES) $(OBJS) daemon.o -o daemon

parttwo:
    $(CC) $(CLIBFLAGS) $(INCLUDES) $(OBJS) server.o -lpthread -o libserver.so.0

bigearsbilly · 07-06-2006, 10:14 AM

Quote:

but my makefile recompiles everything everytime i call it

because that's what you are specifying

firstly, you don't need to specify the CC behaviour, it's built in.
Also your targets have no dependencies.

start with this, see how simple it can be:

Code:

all:daemon server

daemon: daemon.o

server:server.o

you don't need to redifine CC stuff, there are anough flags
for you to use, eg: $(CFLAGS) $(CPPFLAGS) $(LDFLAGS)

make -pns

and grep CC

crabboy · 07-06-2006, 10:51 AM

Simple changes that will fix the dependencies:

Code:

GROUP=groupname
CFLAGS= -g -g3 -ggdb -ggdb3 -O4 -ldl -rdynamic -Wl,-export-dynamic -Wall
CLIBFLAGS= -g -g3 -ggdb -ggdb3 -O4 -fPIC -Wall -Wl,-export-dynamic -shared
CCOMP= -g -g3 -ggdb -ggdb3 -O4 -Wall -fPIC

%.o:    %.cpp
        $(CC) $(CCOMP) $(INCLUDES) -c -o $@ $<


OBJS=utils/classone.o utils/classtwo.o daemon.o server.o

INCLUDES= -Iutils
CC=g++
BINDIR=/usr/local/project

#all:   objects partone parttwo

objects:        $(OBJS)
#objects:
#       $(CC) $(CCOMP) $(INCLUDES) -c utils/classone.cpp -o utils/classone.o
#       $(CC) $(CCOMP) $(INCLUDES) -c utils/classtwo.cpp -o utils/classtwo.o
#       $(CC) $(CCOMP) $(INCLUDES) -c daemon.cpp -o daemon.o
#       $(CC) $(CCOMP) $(INCLUDES) -c server.cpp -o server.o

partone:
        $(CC) $(CFLAGS) $(INCLUDES) $(OBJS) daemon.o -o daemon

parttwo:
        $(CC) $(CLIBFLAGS) $(INCLUDES) $(OBJS) server.o -lpthread -o libserver.so.0

The partone and parttwo are somewhat incorrect. You're specifing the $(OBJS) and the server.o or daemon.o which are included in the OBJS target.

Other changes I'd make to the makefile is creating a seperate makefile for the subdirectory and put the results in a static library. I'd also remove the server.o and daemon.o from the OBJS list. Perhaps you need a DAEMON_OBJ and SERVER_OBJ list of sorts.

crabboy · 07-06-2006, 11:35 AM

...and since I don't feel like working:

utils/Makefile:

Code:

OWNER=username
GROUP=groupname
AR=ar

CC=g++
CCOMP= -g -g3 -ggdb -ggdb3 -O4 -Wall -fPIC

LIB= ../libutils.a

%.o:    %.cpp
        $(CC) $(CCOMP) $(INCLUDES) -c -o $@ $<


OBJS=classone.o classtwo.o

all:    $(LIB)

objects:        $(OBJS)

$(LIB): objects  $(OBJS)
        $(AR) rcs $@ $(OBJS)

clean:
        rm -f $(OBJS) $(LIB)

Base Makefile:

Code:

OWNER=username
GROUP=groupname
CFLAGS= -g -g3 -ggdb -ggdb3 -O4 -ldl -rdynamic -Wl,-export-dynamic -Wall
CLIBFLAGS= -g -g3 -ggdb -ggdb3 -O4 -fPIC -Wall -Wl,-export-dynamic -shared
CCOMP= -g -g3 -ggdb -ggdb3 -O4 -Wall -fPIC

%.o:    %.cpp
        $(CC) $(CCOMP) $(INCLUDES) -c -o $@ $<

.PHONY: dummy

DAEMON_OBJ=daemon.o
SERVER_OBJ=server.o

LIBDIR=.
INCLUDES= -Iutils
LIBS=utils

SHARED=libserver.so.0

CC=g++
BINDIR=/usr/local/project

all:    $(LIBS) daemon shared

$(LIBS):        dummy
        $(MAKE) -C $(LIBS)

daemon: $(DAEMON_OBJ) $(LIBS)
        $(CC) $(CFLAGS) $(INCLUDES) $(DAEMON_OBJ) -L$(LIBDIR) -o $@  -l$(LIBS)

shared:         $(SHARED)

$(SHARED):      $(SERVER_OBJ) $(LIBS)
        $(CC) $(CLIBFLAGS) $(INCLUDES) -L(LIBLIST) $(SERVER_OBJ) -o $@ -lpthread -l$(LIBS)

clean:  dummy
        rm -f *.a $(DAEMON_OBJ) $(SERVER_OBJ)
        $(MAKE) -C $(LIBS) clean

A few more simple changes need to be made to either make it work for a few directories or a tree of sub-directories.