macos C++：在 mac osx 上使用 std::cout 和 gcc
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C++: Using std::cout with gcc on a mac osx
提问by Patof
I'm new to C++ programming and I try to make my first exercise on a mac using gcc in the terminal.
我是 C++ 编程的新手，我尝试在终端中使用 gcc 在 mac 上进行我的第一个练习。
Unfortunately, I can't compile because of issues related to iostream. With a simple program as:
不幸的是，由于与 iostream 相关的问题，我无法编译。用一个简单的程序作为：
#include <iostream>
int main()
{
std::cout << "hello world";
std::cout << endl;
return 0;
}
it gives me the error:
它给了我错误：
error: ‘endl' was not declared in this scope
removing the cout << endl; line gives me these errors:
删除 cout << endl; 行给了我这些错误：
Undefined symbols:
"___gxx_personality_v0", referenced from:
___gxx_personality_v0$non_lazy_ptr in cceBlyS2.o
"std::ios_base::Init::~Init()", referenced from:
___tcf_0 in cceBlyS2.o
"std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)", referenced from:
_main in cceBlyS2.o
"std::ios_base::Init::Init()", referenced from:
__static_initialization_and_destruction_0(int, int)in cceBlyS2.o
"std::cout", referenced from:
__ZSt4cout$non_lazy_ptr in cceBlyS2.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
It's evident that the iostream header is not properly linked. I tried "<"iostream.h">" and "iostream.h" with no success.
很明显，iostream 标头没有正确链接。我尝试了 "<"iostream.h">" 和 "iostream.h"，但没有成功。
Does anybody has any hint that could help me? Thanks!
有人有任何提示可以帮助我吗？谢谢！
回答by Jerry Coffin
You need to use std::endl;-- the entire standard library is in the stdnamespace. It also looks like you used gccinstead of g++on the command line. The latter automatically does the steps necessary to link C++ correctly.
您需要使用std::endl;——整个标准库都在std命名空间中。它看起来也像是您在命令行上使用的gcc而不是g++。后者会自动执行正确链接 C++ 所需的步骤。
回答by Buhake Sindi
endl;falls under the stdnamespace
endl;属于std命名空间
your 2 options are as follows:
您的 2 个选项如下：
1) declaring your namespace, e.g.
1）声明你的命名空间，例如
#include <iostream>
using namespace std;
int main() {
cout << "hello world";
cout << endl;
return 0;
}
or using std::endl;e.g.
或使用std::endl;例如
std::cout << "hello world";
std::cout << std::endl;
return 0;
See which one suits you. I recommend 1) (Check that I didn't do std::coutbecause I've declared my namespace already) as it helps to reduce typing std::everytime.
看看哪一款适合你。我推荐 1)（检查我没有这样做，std::cout因为我已经声明了我的命名空间）因为它有助于减少std::每次输入。
回答by e.James
You just need to use std::endl;. Or, better yet, make use of the handy usingdirective:
您只需要使用std::endl;. 或者，更好的是，使用方便的using指令：
#include <iostream>
using namespace std;
int main()
{
cout << "hello world";
cout << endl;
return 0;
}
