4.编写一个通用的 Makefile :-)

1<. 必须要知道的 shell 命令

include

1<. 解释:

$(shell pwd)

(patsubst(filter %/, $(obj-y)))

(foreachf,(subdir-y),$(f)/built-in.o)

(filter−out(obj-y))

(foreachf,(cur_objs),.$(f).d)

(wildcard(dep_files))

示例代码:

1<. 顶层目录

Makefile

CROSS_COMPILE = arm-linux-
AS      = $(CROSS_COMPILE)as
LD      = $(CROSS_COMPILE)ld
CC      = $(CROSS_COMPILE)gcc
CPP     = $(CC) -E
AR      = $(CROSS_COMPILE)ar
NM      = $(CROSS_COMPILE)nm

STRIP       = $(CROSS_COMPILE)strip
OBJCOPY     = $(CROSS_COMPILE)objcopy
OBJDUMP     = $(CROSS_COMPILE)objdump

export AS LD CC CPP AR NM
export STRIP OBJCOPY OBJDUMP

CFLAGS := -Wall -Werror -O2 -g
CFLAGS += -I $(shell pwd)/include

LDFLAGS := -lm -lfreetype -lts -lpthread -ljpeg

export CFLAGS LDFLAGS

TOPDIR := $(shell pwd)
export TOPDIR

TARGET := digitpi
a095
c

obj-y += main.o
obj-y += display/
obj-y += encoding/
obj-y += fonts/
obj-y += input/
obj-y += debug/
obj-y += render/
obj-y += page/
obj-y += file/

all :
make -C ./ -f $(TOPDIR)/Makefile.build
$(CC) $(LDFLAGS) -o $(TARGET) built-in.o

clean:
rm -f $(shell find -name "*.o")
rm -f $(TARGET)

distclean:
rm -f $(shell find -name "*.o")
rm -f $(shell find -name "*.d")
rm -f $(TARGET)

配置文件 Makefile.build

PHONY := __build
__build:

obj-y :=
subdir-y :=

include Makefile

# obj-y := a.o b.o c/ d/
# $(filter %/, $(obj-y))   : c/ d/
# __subdir-y  : c d
# subdir-y    : c d
__subdir-y  := $(patsubst %/,%,$(filter %/, $(obj-y)))
subdir-y    += $(__subdir-y)

# c/built-in.o d/built-in.o
subdir_objs := $(foreach f,$(subdir-y),$(f)/built-in.o)

# a.o b.o
cur_objs := $(filter-out %/, $(obj-y))
dep_files := $(foreach f,$(cur_objs),.$(f).d)
dep_files := $(wildcard $(dep_files))

ifneq ($(dep_files),)
include $(dep_files)
endif

PHONY += $(subdir-y)

__build : $(subdir-y) built-in.o

$(subdir-y):
make -C $@ -f $(TOPDIR)/Makefile.build

built-in.o : $(cur_objs) $(subdir_objs)
$(LD) -r -o $@ $^

dep_file = .$@.d

%.o : %.c
$(CC) $(CFLAGS) -Wp,-MD,$(dep_file) -c -o $@ $<

.PHONY : $(PHONY)

2<. 子目录下的 Makefile

obj-y += page_manager.o
obj-y += main_page.o
obj-y += setting_page.o
obj-y += interval_page.o
obj-y += browse_page.o
obj-y += auto_page.o
obj-y += manual_page.o