C++ iostream 链接器错误
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iostream linker error
提问by Steve
I have some old C code that I would like to combine with some C++ code.
我有一些旧的 C 代码，我想将它们与一些 C++ 代码结合起来。
The C code used to have has the following includes:
过去的 C 代码包括以下内容：
#include <windows.h>
#include <stdio.h>
#include <string.h>
#include "mysql.h"
Now I'm trying to make it use C++ with iostream like this:
现在我试图让它像这样使用 C++ 和 iostream：
#include <windows.h>
#include <stdio.h>
#include <string>
#include <iostream>
#include "mysql.h"
But I keep getting the following linker errors when I compile:
但是我在编译时不断收到以下链接器错误：
[Linker error] undefined reference to `std::string::size() const'
[Linker error] undefined reference to `std::string::operator[](unsigned int) const'
[Linker error] undefined reference to `std::string::operator[](unsigned int) const'
[Linker error] undefined reference to `std::string::operator[](unsigned int) const'
[Linker error] undefined reference to `std::ios_base::Init::Init()'
[Linker error] undefined reference to `std::ios_base::Init::~Init()'
ld returned 1 exit status
[链接器错误] 未定义对 `std::string::size() const' 的引用
[链接器错误] 未定义对`std::string::operator[](unsigned int) const'的引用
[链接器错误] 未定义对`std::string::operator[](unsigned int) const'的引用
[链接器错误] 未定义对`std::string::operator[](unsigned int) const'的引用
[链接器错误] 未定义对 `std::ios_base::Init::Init()' 的引用
[链接器错误] 未定义对 `std::ios_base::Init::~Init()' 的引用
ld 返回 1 个退出状态
How do I resolve this?
我该如何解决？
Edit: My compiler is Dev-C++ 4.9.9.2
编辑：我的编译器是 Dev-C++ 4.9.9.2
回答by Max Lybbert
The C string.hheader and the C++ stringheader are not interchangeable.
Cstring.h头文件和 C++string头文件不可互换。
Overall, though, your problem is that the file is getting properly compiled, but the wrong runtime library is getting linked in.
不过，总的来说，您的问题是文件得到了正确编译，但错误的运行时库被链接到了。
Dev-C++ uses GCC. GCC can correctly determine the language in a file based on file extension, but won't link the right runtime library in unless you specifically ask it to (-lstdc++ at the command line). Calling GCC as "g++" (or, in your case, "mingwin32-g++") will also get the right language and will link the needed library.
Dev-C++ 使用 GCC。GCC 可以根据文件扩展名正确确定文件中的语言，但不会链接正确的运行时库，除非您特别要求它（命令行中的 -lstdc++）。将 GCC 称为“g++”（或者，在您的情况下为“mingwin32-g++”）也将获得正确的语言并链接所需的库。
回答by Mike G.
You need to link against your C++ runtime. It depends on your platform and compiler, but adding -lC to your linkline might do it.
您需要链接到您的 C++ 运行时。这取决于您的平台和编译器，但将 -lC 添加到您的链接行可能会这样做。
So might linking using your C++ compiler rather than ld.
所以可能会使用 C++ 编译器而不是 ld 进行链接。
In any case, you probably have to link using the C++ compiler rather than ld if you want your C++ code to work correctly -- it's often required for exceptions and static initializers to work correctly...
在任何情况下，如果您希望 C++ 代码正常工作，您可能必须使用 C++ 编译器而不是 ld 进行链接——通常需要异常和静态初始化程序才能正常工作......
回答by Amaresh
I got the same exact error when i was trying to compile with Cygwin (g++).
当我尝试使用 Cygwin (g++) 进行编译时，我遇到了完全相同的错误。
just add -L/usr/local/bin -L/usr/libin the compilation rules and it should work.
只需添加-L/usr/local/bin -L/usr/lib编译规则，它应该可以工作。
This may be specific to Cygwin but it might help solve your problem too.
这可能是 Cygwin 特有的，但它也可能有助于解决您的问题。
