macos osx 上的编译错误“未定义符号”
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Compilation error "Undefined symbols" on osx
提问by Anthony Kong
I am trying out a very simple cpp program on osx just to get myself familiar with the osx platform, so I am very surprised to encounter any error message.
我正在 osx 上尝试一个非常简单的 cpp 程序只是为了让自己熟悉 osx 平台，所以我很惊讶遇到任何错误消息。
Here is the code:
这是代码：
#include <iostream>
using namespace std;
int main() {
cout << "Hello, world!" << endl;
return 0;
}
I compile it by running
我通过运行编译它
gcc -Wall hello.cpp -o hello
Then I get this 'undefined symbols' message:
然后我收到此“未定义符号”消息：
Undefined symbols:
"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 ccA9oElQ.o
"std::ios_base::Init::Init()", referenced from:
__static_initialization_and_destruction_0(int, int)in ccA9oElQ.o
"std::basic_string<char, std::char_traits<char>, std::allocator<char> >::size() const", referenced from:
std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccA9oElQ.o
"std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long) const", referenced from:
std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccA9oElQ.o
std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccA9oElQ.o
std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccA9oElQ.o
"___gxx_personality_v0", referenced from:
std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccA9oElQ.o
_main in ccA9oElQ.o
___tcf_0 in ccA9oElQ.o
unsigned long const& std::min<unsigned long>(unsigned long const&, unsigned long const&)in ccA9oElQ.o
__static_initialization_and_destruction_0(int, int)in ccA9oElQ.o
global constructors keyed to mainin ccA9oElQ.o
CIE in ccA9oElQ.o
"std::ios_base::Init::~Init()", referenced from:
___tcf_0 in ccA9oElQ.o
"std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)", referenced from:
_main in ccA9oElQ.o
"std::basic_ostream<char, std::char_traits<char> >::operator<<(std::basic_ostream<char, std::char_traits<char> >& (*)(std::basic_ostream<char, std::char_traits<char> >&))", referenced from:
_main in ccA9oElQ.o
"std::cout", referenced from:
_main in ccA9oElQ.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
I do not know if it is related: I have both xcode 3 and xcode 4 installed on my MBP
我不知道它是否相关：我的 MBP 上同时安装了 xcode 3 和 xcode 4
Here is the version information:
以下是版本信息：
$ gcc -v
Using built-in specs.
Target: i686-apple-darwin10
Configured with: /var/tmp/gcc/gcc-5666.3~6/src/configure --disable-checking --enable-werror --prefix=/usr --mandir=/share/man --enable-languages=c,objc,c++,obj-c++ --program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib --build=i686-apple-darwin10 --program-prefix=i686-apple-darwin10- --host=x86_64-apple-darwin10 --target=i686-apple-darwin10 --with-gxx-include-dir=/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Apple Inc. build 5666) (dot 3)
System information
系统信息
$ uname -a
Darwin mbp002.local 10.7.0 Darwin Kernel Version 10.7.0: Sat Jan 29 15:17:16 PST 2011; root:xnu-1504.9.37~1/RELEASE_I386 i386
回答by
Use g++instead of gccsince you're compiling a C++ program:
使用g++而不是gcc因为您正在编译 C++ 程序：
g++ -Wall hello.cpp -o hello
Alternatively, use clang++since Apple haven't updated GCC in a while and it's unlikely they'll ever update it:
或者，使用clang++Apple 已经有一段时间没有更新 GCC 并且他们不太可能更新它：
clang++ -Wall hello.cpp -o hello
回答by Anthony Kong
Run it using g++
使用 g++ 运行它
g++ -Wall hello.cpp -o hello
If you use gcc, the C++ libraries are not linked in by default.
如果您使用 gcc，默认情况下不会链接 C++ 库。
