在ubuntu vim下编辑如下代码（代码来自《C++标准程序库》p107）：
#include < iostream > #include < vector > #include < string > #include < algorithm > #include < iterator > using namespace std; int main(){ vector < string > coll; /* read all words from the standard input * - source: all strings until end-of-file (or erro) * - destination: coll(inserting) */ copy (istream_iterator < string > (cin), // start of source istream_iterator < string > (), // end of source back_inserter(coll)); // sort elements sort (coll.begin(), coll.end()); /* print all elements without duplicates * - source: coll * - destination: standard output (with newline between elements) */ unique_copy (coll.begin(), coll.end(), // source ostream_iterator < string > (cout, " \n " )); // destination return 0 ;}
使用GCC编译后出现下列可怕的问题：
hello.o: In function `main ' : hello.cpp:(.text + 0x41 ): undefined reference to `std::cin ' hello.cpp:(.text + 0xd1 ): undefined reference to `std::cout ' hello.o: In function `__static_initialization_and_destruction_0( int , int ) ' : hello.cpp:(.text + 0x19e ): undefined reference to `std::ios_base::Init::Init() ' hello.cpp:(.text + 0x1a3 ): undefined reference to `std::ios_base::Init:: ~ Init() ' hello.o: In function `std::istream_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , char , std::char_traits < char > , int > :: ~ istream_iterator() ' : hello.cpp:(.text._ZNSt16istream_iteratorISscSt11char_traitsIcEiED2Ev[_ZNSt16istream_iteratorISscSt11char_traitsIcEiED5Ev] + 0x10 ): undefined reference to `std::basic_string < char , std::char_traits < char > , std::allocator < char > > :: ~ basic_string() ' hello.o: In function `std::istream_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , char , std::char_traits < char > , int > ::istream_iterator(std::basic_istream < char , std::char_traits < char > >& ) ' : hello.cpp:(.text._ZNSt16istream_iteratorISscSt11char_traitsIcEiEC2ERSi[_ZNSt16istream_iteratorISscSt11char_traitsIcEiEC5ERSi] + 0x24 ): undefined reference to `std::basic_string < char , std::char_traits < char > , std::allocator < char > > ::basic_string() ' hello.cpp:(.text._ZNSt16istream_iteratorISscSt11char_traitsIcEiEC2ERSi[_ZNSt16istream_iteratorISscSt11char_traitsIcEiEC5ERSi] + 0x41 ): undefined reference to `std::basic_string < char , std::char_traits < char > , std::allocator < char > > :: ~ basic_string() ' hello.o: In function `std::istream_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , char , std::char_traits < char > , int > ::istream_iterator() ' : hello.cpp:(.text._ZNSt16istream_iteratorISscSt11char_traitsIcEiEC2Ev[_ZNSt16istream_iteratorISscSt11char_traitsIcEiEC5Ev] + 0x24 ): undefined reference to `std::basic_string < char , std::char_traits < char > , std::allocator < char > > ::basic_string() ' hello.o: In function `std::istream_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , char , std::char_traits < char > , int > ::istream_iterator(std::istream_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , char , std::char_traits < char > , int > const & ) ' : hello.cpp:(.text._ZNSt16istream_iteratorISscSt11char_traitsIcEiEC2ERKS2_[_ZNSt16istream_iteratorISscSt11char_traitsIcEiEC5ERKS2_] + 0x2f ): undefined reference to `std::basic_string < char , std::char_traits < char > , std::allocator < char > > ::basic_string(std::basic_string < char , std::char_traits < char > , std::allocator < char > > const & ) ' hello.o: In function `std::istream_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , char , std::char_traits < char > , int > ::_M_read() ' : hello.cpp:(.text._ZNSt16istream_iteratorISscSt11char_traitsIcEiE7_M_readEv[std::istream_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , char , std::char_traits < char > , int > ::_M_read()] + 0x29 ): undefined reference to `std::basic_ios < char , std::char_traits < char > > :: operator void * () const ' hello.cpp:(.text._ZNSt16istream_iteratorISscSt11char_traitsIcEiE7_M_readEv[std::istream_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , char , std::char_traits < char > , int > ::_M_read()] + 0x61 ): undefined reference to `std::basic_istream < char , std::char_traits < char > >& std:: operator >>< char , std::char_traits < char > , std::allocator < char > > (std::basic_istream < char , std::char_traits < char > >& , std::basic_string < char , std::char_traits < char > , std::allocator < char > >& ) ' hello.cpp:(.text._ZNSt16istream_iteratorISscSt11char_traitsIcEiE7_M_readEv[std::istream_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , char , std::char_traits < char > , int > ::_M_read()] + 0x7f ): undefined reference to `std::basic_ios < char , std::char_traits < char > > :: operator void * () const ' hello.o: In function ` void std::__insertion_sort < __gnu_cxx::__normal_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > >* , std::vector < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , std::allocator < std::basic_string < char , std::char_traits < char > , std::allocator < char > > > > > > (__gnu_cxx::__normal_iterator < std::basic_string < char , std::char_traits < char > , std::allocator < char > >* , std::vector < std::basic_string < char , std::char_traits < char > , std::allocator < char > > , std::allocator < std::basic_string < char , std::char_traits < char > , ……
但是使用Code::Blocks编译、链接可以通过，不解，上网搜了一下。
网上的解释是：“ you need to add -lstdc++, or use 'g++' rather than 'gcc' as your driver program.”，也就是说如果想要使用g++编译程序的话，那么链接时需要添加“-Istdc++”。
我试了一下 ， 在链接时加上"-Istdc++"，就没有问题了。
关于g++，让我想起了，在ubuntu下一开始安装完code::blocks的时候，提示需要安装g++。原来code::blocks内置编译器使用的是g++，但是为什么在建工程的时候，提示使用的编译器是gcc呢？？
这就引来了一个问题：“gcc和g++的区别和联系是什么？”网上搜了一下“gcc和g++”（http://www.yuanma.org/data/2007/0406/article_2498.htm），整理下来有这么几条是有用的：
（1）gcc和g++都是GNU(组织)的一个编译器。
（2）后缀名为.c的程序和.cpp的程序g++都会当成是c++的源程序来处理。而gcc不然，gcc会把.c的程序处理成c程序。
（3）对于.cpp的程序，编译可以用gcc/g++，而链接可以用g++或者gcc -lstdc++。（个人觉得这条是最重要的）
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