Question

I’m writing a makefile framework for a project. Say, I have a main.c in the top dir, and many subdirs each containing a C file. To link all the object files togoter, I assign a initial value in the top makefile:

export TARGET_LIST := main.o

And in each subdirs, I append them to the list:

# sub1/Makefile
TARGET := a.o                                                                                                                                                          
TARGET_LIST += $(TARGET)

When return to the top dir, the TARGET_LIST is still with main.o. I’m sure all subdirs are entered. Is there any good way to do this?

The top makefile:

all: main

export TOP_DIR = $(shell pwd)
export TARGET_LIST := main.o
SUBDIRS := a b c d

CFLAGS := -Iinc

all:main

main:main.o subdirs
        cc $(TARGET_LIST) -o $@ $(CFLAGS)

subdirs: $(patsubst %, _dir_%, $(SUBDIRS))

$(patsubst %, _dir_%, $(SUBDIRS)) :
        $(MAKE) -C $(patsubst _dir_%, %, $@) $(TGT)

The Rules.make:

all:$(TARGET)

%.o:%.c
        @echo $(TARGET_LIST)
        $(CC) -c $^ -o $@ $(CFLAGS) $(LDFLAGS)

The subdir makefile:

TARGET := a.o
TARGET_LIST += $(TARGET)
CFLAGS := 
LDFLAGS := 

include $(TOP_DIR)/Rules.make

Answer 1

Do yourself the favour, and use a high-level build system if you can. Almost anything is better than hand-written Makefiles. E.g. CMake, SCons or waf are some of the more popular alternatives.