makefile 编译本目录下所有cpp文件，包括子目录

#
#  ======== makefile ========
#
CC = gcc
CXX = g++
CFLAG = -g -O2 -std=c++0x -Wno-deprecated  #-Wall
LIBS  = -lm -lstdc++ 
EXCUTABLE_FILE = test_main

TEST_SUBDIR=./test_subdir/
SOURCE=$(wildcard ./*cpp $(TEST_SUBDIR)*.cpp)
INCLUDE = -I ./test_subdir/ -I ./

OBJECTS=$(patsubst %.cpp,%.o,$(SOURCE))
$(EXCUTABLE_FILE) : $(OBJECTS)
    $(CXX) $(INCLUDE) $(CFLAG) $^ -o $@ $(LIBS)
$(OBJECTS):%.o : %.cpp
    $(CXX) $(INCLUDE) -c $(CFLAG) $< -o $@ $(LIBS)

.PHONY:clean
clean:
    rm -rf $(OBJECTS) $(EXCUTABLE_FILE)

关键点解释：
其中wildcard和patsubst为makefile关键字,

• $(wildcard .cpp /xxx/xxx/.cpp) 为获取当前目录下和/xxx/xxx/目录下所有.cpp文件名;
• $(patsubst$(SRCS)) 为替换所有的.cpp后缀文件名为.o后缀;
• %.o : %.cpp 表示将所有的[.cpp]文件编译为[.o]文件;

目录结构