Makefile: use multiple makefiles

Question

I have a project that has many makefiles inside it. Because sometimes I need to compile only some parts of my project so I decided to have one makefile in each directory. But when I want to run the main makefile that includes all other ones to compile my project it gives me lots of errors. This is my project tree:

root 'makefile'

-folder1 'foo1.c foo2.c makefile'

-folder2 'makefile'

--folder2-1 'foo3.c foo4.c makefile'

--folder2-2 'foo5.c makefile'

Each makefile in the very last directory has been included to it's upper makefile. But it doesn't run the main makefile. I'm really new to GNU make and I want to have something like this but I don't know how. I just wrote some make scripts but it doesn't work. I just want to have something that I can compile the projects parts separately or compile the whole project using multiple makefiles.

Answer 1

any way, I show you something and hope can help you:

all:
    @$(MAKE) -C subfolder

or if you want to use *.mk as your sub makefile, you can write:

all:
    @$(MAKE) -C busfolder -f somename.mk

I show you my example, my DIR looks like:

TOPDIR-- Makefile
|
|-- debug
|   |-- debug.c
|   |-- debug.h
|   |-- debug.mk
|   |-- instrument.c
|   `-- uart_print.c
|-- driver
|   |-- driver.c
|   |-- driver_ddi.c
|   |-- driver_ddi.h
|   |-- driver.h
|   `-- driver.mk
|-- include
|   `-- common.h
|-- Makefile
|-- mw
|   |-- manager.c
|   `-- mw.mk
|-- root
|   |-- main.c
|   `-- root.mk

and my TOP makefile looks like:

MAKE_DIR = $(PWD)

ROOT_DIR    := $(MAKE_DIR)/root 
DRV_DIR     := $(MAKE_DIR)/driver
INCLUDE_DIR := $(MAKE_DIR)/include
DEBUG_DIR   := $(MAKE_DIR)/debug

INC_SRCH_PATH := 
INC_SRCH_PATH += -I$(ROOT_DIR)
INC_SRCH_PATH += -I$(DRV_DIR) 
INC_SRCH_PATH += -I$(INCLUDE_DIR)
INC_SRCH_PATH += -I$(DEBUG_DIR)

LIB_SRCH_PATH :=
LIB_SRCH_PATH += -L$(MAKE_DIR)/libs


COLOR_ON = color
COLOR_OFF = 
CC = $(COLOR_ON)gcc
#CC = $(COLOR_OFF)gcc
LD = ld

LINT = splint

LIBS := -ldriver -ldebug -lmw -lm -lpthread

CFLAGS :=
CFLAGS += $(INC_SRCH_PATH) $(LIB_SRCH_PATH) 
CFLAGS += -Wall -O -ggdb -Wstrict-prototypes -Wno-pointer-sign -finstrument-functions -fdump-rtl-expand
CFLAGS += -DDEBUG -D_REENTRANT

LDFLAGS :=

export MAKE_DIR CC LD CFLAGS LDFLAGS LIBS LINT INC_SRCH_PATH

all:
    @$(MAKE) -C debug -f debug.mk
    @$(MAKE) -C driver -f driver.mk
    @$(MAKE) -C mw -f mw.mk
    @$(MAKE) -C root -f root.mk

.PHONY: clean
clean:
    @$(MAKE) -C debug -f debug.mk clean
    @$(MAKE) -C driver -f driver.mk clean
    @$(MAKE) -C mw -f mw.mk clean
    @$(MAKE) -C root -f root.mk clean

it will call sub DIR *.mk during the compile. The sub DIR makefile, I just write a simple example for you reference:

LIB = $(MAKE_DIR)/libs/yourmodulename.a
SRCS = $(wildcard *.c)
OBJS = $(patsubst %.c, %.o, $(SRCS))

$(LIB): $(OBJS)
    @mkdir -p ../libs
    @$(AR) cr $@ $^
    @echo "    Archive    $(notdir $@)"

$(OBJS): $(SRCS)
    @$(CC) $(CFLAGS) -c $^
    @echo "    CC        $(OBJS)"

.PHONY: clean
clean:
    @$(RM) -f $(LIB) $(OBJS)
    @$(RM) -f *.expand
    @echo "    Remove Objects:   $(OBJS)"

for the makefile, which generate the final target file(like a.out) is little bit different, because I use the sub makefile to generate LIB file, and I use a root.mk to generate final target:

PROG = ../prog/DEMO

SRCS = $(wildcard *.c)
OBJS = $(patsubst %.c, %.o, $(SRCS))

$(PROG): $(SRCS)
    @mkdir -p ../prog
    @$(CC) $^ $(CFLAGS) -Wl,-Map=$(PROG).map $(LIBS) -o $@
    @echo "    Generate Program $(notdir $(PROG)) from $^"

.PHONY: clean
clean:
    @$(RM) -f $(OBJS) $(PROG)
    @$(RM) -f *.expand
    @$(RM) -rf ../prog ../libs
    @echo "    Remove Objects:   $(OBJS)"
    @echo "    Remove Libraries:  $(notdir $(PROG))"