什么是 Makefile ？ （适用于 Boost项目）

Makefile背后的根 递归 思想是：

要建立目标，我们需要 先决条件 （其他目标！）和建立 指示

先决条件

它们是文件，文件夹或伪造的目标（通常在中.PHONY）。测试文件/文件夹的存在和修改日期。

如果目标没有任何先决条件或比任何先决条件还旧，则需要重新构建目标。

指令

指令是 shell命令 ，从一个选项卡开始。每条指令行都是一个shell实例。当当前命令以反斜杠结尾时，可以在下一行继续执行shell命令\。

目标定义

目标是 依赖关系 或 规则 。

依赖关系：

target : prerequisite1 prerequisite2 prerequisiteN

规则：

target : prerequisite1 prerequisite2 prerequisiteN
    instructions1
    @hidden_batch1 ; \
  hidden_batch2

在说明开始前带有选项卡。

除错

调试Makefile可能会让人头疼。尝试在Makefile中执行以下操作以显示跟踪（带有的文件和行位置warning）：

$(info Shell: $(SHELL))
$(warning CXX: $(CXX))

当您的Makefile包含很多嵌套if/else/endif并且您不确定当前路径是什么时，这将很有用。

Makefile结构

理想的makefile结构为：

1. 变量设置
2. 目标/依赖声明

一旦了解了整个Makefile及其包含文件（存储在make内部数据库中），便开始真正的目标指令处理。

例

最后，使用Boost将理论应用于该特定示例，并创建伪造的源文件进行说明。

rawr.cpp

#include "rawr.h"

simple_ls.cpp

#include "rawr.h"

converter.cpp

#include <iostream>

#include "rawr.h"
#include "simple_ls.h"
#include "2dquicksort.h"

#include <boost/array.hpp>   // Boost!

int main(int argc, char **argv)
{
    boost::array<int,4> a = { { 1, 2, 3, 4} };
    std::cout << a[1] << std::endl;
    return 0;
}

生成文件

如果您Makefile从 stack overflow 复制源，请不要忘记用真实的Tab代替空格：

sed -i~ -e 's/^    /\t/' Makefile

Makefile来源：

## Makefile for C++ project using Boost
#
# @author Cedric "levif" Le Dillau
#
# Some notes:
# - Using ':=' instead of '=' assign the value at Makefile parsing time,
#   others are evaluated at usage time. This discards
# - Use ':set list' in Vi/Vim to show tabs (Ctrl-v-i force tab insertion)
#

# List to '.PHONY' all fake targets, those that are neither files nor folders.
# "all" and "clean" are good candidates.
.PHONY: all, clean

# Define the final program name
PROGNAME := converter

# Pre-processor flags to be used for includes (-I) and defines (-D) 
CPPFLAGS := -DUSE_BOOST

# CFLAGS is used for C compilation options.
CFLAGS := -Wall -O0

# CXXFLAGS is used for C++ compilation options.
CXXFLAGS += -Wall -O0

# LDFLAGS is used for linker (-g enables debug symbols)
LDFLAGS  += -g

# Which Boost modules to use (all)
BOOST_MODULES = \
  date_time     \
  filesystem    \
  graph         \
  iostreams     \
  math_c99      \
  system        \
  serialization \
  regex

# Boost libraries' type (a suffix)
BOOST_MODULES_TYPE := -mt

# Define library names with their type
BOOST_MODULES_LIBS := $(addsuffix $(BOOT_MODULES_TYPE),$(BOOST_MODULES))

# Define the linker argument to use the Boost libraries.
BOOST_LDFLAGS := $(addprefix -lboost_,$(BOOST_MODULES_LIBS))

# Feed compiler/linker flags with Boost's
CPPFLAGS += $(BOOST_CPPFLAGS)
LDFLAGS += $(BOOST_LDFLAGS)

# List the project' sources to compile or let the Makefile recognize
# them for you using 'wildcard' function.
#
#SOURCES = simple_ls.cpp rawr.cpp converter.cpp
SOURCES = $(wildcard *.cpp)

# List the project' headers or let the Makefile recognize
# them for you using 'wildcard' function.
#
#HEADERS = simple_ls.h 2dquicksort.h rawr.h
HEADERS = $(wildcard %.h)

# Construct the list of object files based on source files using
# simple extension substitution.
OBJECTS = $(SOURCES:%.cpp=%.o)

#
# Now declare the dependencies rules and targets
#
# Starting with 'all' make it  becomes the default target when none 
# is specified on 'make' command line.
all : $(PROGNAME)

# Declare that the final program depends on all objects and the Makfile
$(PROGNAME) : $(OBJECTS) Makefile
    $(CXX) -o $@ $(LDFLAGS) $(OBJECTS)

# Now the choice of using implicit rules or not (my choice)...
#
# Choice 1: use implicit rules and then we only need to add some dependencies
#           to each object.
#
## Tells make that each object file depends on all headers and this Makefile.
#$(OBJECTS) : $(HEADERS) Makefile
#
# Choice 2: don't use implicit rules and specify our will
%.o: %.cpp $(HEADERS) Makefile
    $(CXX) $(CXXFLAGS) $(CPPFLAGS) -c $(OUTPUT_OPTION) $<

# Simple clean-up target
# notes:
# - the '@' before 'echo' informs make to hide command invocation.
# - the '-' before 'rm' command to informs make to ignore errors.
clean :
    @echo "Clean."
    -rm -f *.o $(PROGNAME)

档案清单

2dquicksort.h
converter.cpp
Makefile
rawr.cpp
rawr.h
simple_ls.cpp
simple_ls.h

汇编

make clean all
Clean.
rm -f *.o converter
g++ -Wall -O0 -DUSE_BOOST  -c -o converter.o converter.cpp
g++ -Wall -O0 -DUSE_BOOST  -c -o rawr.o rawr.cpp
g++ -Wall -O0 -DUSE_BOOST  -c -o simple_ls.o simple_ls.cpp
g++ -o converter -g -lboost_date_time -lboost_filesystem -lboost_graph -lboost_iostreams -lboost_math_c99 -lboost_system -lboost_serialization -lboost_regex converter.o rawr.o simple_ls.o

结果

现在，几乎是最小的Boost程序的结果：

./converter
2

没有理由不使用它！ Boost 实际上是功能强大的C ++工具箱:)