Linux Makefile编写之可执行程序

1 概述

编译工具有很多(make/cmake/BJam)。如果不考虑跨平台的话，还是make比较方便。使用make编译需要编写Makefile。本文编写Makefile来生成C/C++可执行程序。

2 Makefile文件命名

Makefile文件首先是一个文本文件，Linux下默认有两种命名方式:

Makefile 这是最常用的命名方式
makefile 这是优先级高的命名方式

在工程目录下运行make命令，make程序先找makefile，如果没有makefile再找Makefile文件。也就是说如果makefile和Makefile两个文件都存在默认使用makefile。

其实Makefile的文件名可以是任意的，例如Buildfile，可以使用下面命令编译：

make -f BuildFile

本文使用make程序版本:

$make --version
GNU Make 4.2.1
Built for x86_64-pc-linux-gnu
Copyright (C) 1988-2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

3 MakeFile实例

这里以CppTest库测试代码为例，代码目录结构：

cpptest2.0.0$ tree
.
├── Makefile
├── cpptest
│   ├── Makefile
│   ├── inc
│   │   ├── cpptest-assert.h
│   │   ├── cpptest-collectoroutput.h
│   │   ├── cpptest-compileroutput.h
│   │   ├── cpptest-htmloutput.h
│   │   ├── cpptest-output.h
│   │   ├── cpptest-source.h
│   │   ├── cpptest-suite.h
│   │   ├── cpptest-textoutput.h
│   │   ├── cpptest-time.h
│   │   └── cpptest.h
│   └── src
│       ├── collectoroutput.cpp
│       ├── compileroutput.cpp
│       ├── config.h
│       ├── htmloutput.cpp
│       ├── missing.cpp
│       ├── missing.h
│       ├── source.cpp
│       ├── suite.cpp
│       ├── textoutput.cpp
│       ├── time.cpp
│       ├── utils.cpp
│       ├── utils.h
│       └── winconfig.h
└── test
    ├── Makefile
    └── mytest.cpp

4 directories, 27 files

3.1 Makefile

all:
	@make -C cpptest
	@make -C test

clean:
	@make -C cpptest clean
	@make -C test clean

.PHNOY: all clean

说明：

根目录Makefile调用cpptest和test目录下Makefile进行编译。

3.2 cpptest/Makefile

参考上一篇文章Linux Makefile编写之静态库

3.3 test/Makefile

PROJECT_NAME ?= test
PWD := $(shell pwd)
TOP := $(PWD)/..
INCS :=  -I$(TOP)/cpptest/inc
SRCDIR := $(PWD)
BINDIR := $(TOP)/bin
LIBS := $(TOP)/cpptest/lib/libcpptest.a
APPNAME := $(BINDIR)/$(PROJECT_NAME)

CC ?= gcc
CXX ?= g++

CFLAGS := 
C++FLAGS := -std=c++11
LINKFLAGS := 

CSRC := $(wildcard $(SRCDIR)/*.c)
OBJS := $(patsubst %.c,%.o,$(CSRC))

CPPS := $(wildcard $(SRCDIR)/*.cpp)
CPPOBJS := $(patsubst %.cpp,%.o,$(CPPS))

all: $(OBJS) $(CPPOBJS) $(BINDIR)
	$(CXX) $(OBJS) $(CPPOBJS) $(LIBS) $(LINKFLAGS) -o $(APPNAME)

$(OBJS): %.o:%.c
	$(CC) -c $(CFLAGS) $(INCS) $< -o $@

$(CPPOBJS): %.o:%.cpp
	$(CXX) -c $(C++FLAGS) $(INCS) $< -o $@

$(BINDIR):
	@mkdir -p $(BINDIR)

.PHNOY:clean
clean:
	@rm -f $(OBJS) $(CPPOBJS)
	@rm -f $(APPNAME)

3.4

编译结果:

make[1]: Entering directory '/home/james/git/cpptest2.0.0/cpptest'
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/cpptest/inc /home/james/git/cpptest2.0.0/cpptest/src/utils.cpp -o /home/james/git/cpptest2.0.0/cpptest/src/utils.o
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/cpptest/inc /home/james/git/cpptest2.0.0/cpptest/src/source.cpp -o /home/james/git/cpptest2.0.0/cpptest/src/source.o
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/cpptest/inc /home/james/git/cpptest2.0.0/cpptest/src/time.cpp -o /home/james/git/cpptest2.0.0/cpptest/src/time.o
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/cpptest/inc /home/james/git/cpptest2.0.0/cpptest/src/collectoroutput.cpp -o /home/james/git/cpptest2.0.0/cpptest/src/collectoroutput.o
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/cpptest/inc /home/james/git/cpptest2.0.0/cpptest/src/textoutput.cpp -o /home/james/git/cpptest2.0.0/cpptest/src/textoutput.o
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/cpptest/inc /home/james/git/cpptest2.0.0/cpptest/src/compileroutput.cpp -o /home/james/git/cpptest2.0.0/cpptest/src/compileroutput.o
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/cpptest/inc /home/james/git/cpptest2.0.0/cpptest/src/htmloutput.cpp -o /home/james/git/cpptest2.0.0/cpptest/src/htmloutput.o
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/cpptest/inc /home/james/git/cpptest2.0.0/cpptest/src/suite.cpp -o /home/james/git/cpptest2.0.0/cpptest/src/suite.o
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/cpptest/inc /home/james/git/cpptest2.0.0/cpptest/src/missing.cpp -o /home/james/git/cpptest2.0.0/cpptest/src/missing.o
ar -rcD /home/james/git/cpptest2.0.0/cpptest/lib/libcpptest.a  /home/james/git/cpptest2.0.0/cpptest/src/utils.o /home/james/git/cpptest2.0.0/cpptest/src/source.o /home/james/git/cpptest2.0.0/cpptest/src/time.o /home/james/git/cpptest2.0.0/cpptest/src/collectoroutput.o /home/james/git/cpptest2.0.0/cpptest/src/textoutput.o /home/james/git/cpptest2.0.0/cpptest/src/compileroutput.o /home/james/git/cpptest2.0.0/cpptest/src/htmloutput.o /home/james/git/cpptest2.0.0/cpptest/src/suite.o /home/james/git/cpptest2.0.0/cpptest/src/missing.o
make[1]: Leaving directory '/home/james/git/cpptest2.0.0/cpptest'
make[1]: Entering directory '/home/james/git/cpptest2.0.0/test'
g++ -c -std=c++11 -I/home/james/git/cpptest2.0.0/test/../cpptest/inc /home/james/git/cpptest2.0.0/test/mytest.cpp -o /home/james/git/cpptest2.0.0/test/mytest.o
g++  /home/james/git/cpptest2.0.0/test/mytest.o /home/james/git/cpptest2.0.0/test/../cpptest/lib/libcpptest.a  -o /home/james/git/cpptest2.0.0/test/../bin/test
make[1]: Leaving directory '/home/james/git/cpptest2.0.0/test'

说明:

编译生成静态库libcpptes.a文件放在cpptest/lib目录下
编译生成可执行程序放bin目录下
编译生成.o与源码在同一目录

4 代码分析

4.1 定义工程名及路径

PROJECT_NAME ?= test

PWD := $(shell pwd)
TOP := $(PWD)/..
INCS :=  -I$(TOP)/cpptest/inc
SRCDIR := $(PWD)
BINDIR := $(TOP)/bin
LIBS := $(TOP)/cpptest/lib/libcpptest.a
APPNAME := $(BINDIR)/$(PROJECT_NAME)

说明:

定义工程名
调用shell命令pwd获取当前路径PWD
利用PWD定义include/src/bin路径
定义依赖库名称
定义可执行程序名称

4.2 定义编译器及选项

CC ?= gcc
CXX ?= g++

CFLAGS := 
C++FLAGS := -std=c++11
LINKFLAGS :=

说明：

定义C/C++编译器名称
定义C/C++编译选项，C++使用C++11标准。
定义链接选项LINKFLAGS

4.3 自动选择译源文件

CSRC := $(wildcard $(SRCDIR)/*.c)
OBJS := $(patsubst %.c,%.o,$(CSRC))

CPPS := $(wildcard $(SRCDIR)/*.cpp)
CPPOBJS := $(patsubst %.cpp,%.o,$(CPPS))

说明:

调用函数wildcard扫描src下所有.c/.cpp文件
调用函数patsubst通过源文件生成.o目标文件

4.4 编译依赖项

all: $(OBJS) $(CPPOBJS) $(BINDIR)
	$(CXX) $(OBJS) $(CPPOBJS) $(LIBS) $(LINKFLAGS) -o $(APPNAME)

$(OBJS): %.o:%.c
	$(CC) -c $(CFLAGS) $(INCS) $< -o $@

$(CPPOBJS): %.o:%.cpp
	$(CXX) -c $(C++FLAGS) $(INCS) $< -o $@

$(BINDIR):
	@mkdir -p $(BINDIR)

.PHNOY:clean
clean:
	@rm -f $(OBJS) $(CPPOBJS)
	@rm -f $(APPNAME)

说明: