Linux 错误 C2375：重新定义；不同的联系
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error C2375: redefinition; different linkage
提问by CarolusPl
Error place in api:
api 中的错误位置：
#define DLLEXPORT extern "C" __declspec(dllexport)
DLLEXPORT int CAnyseeUSBTVControllerDlg::InitCaptureDevice()
{
In my .h library class and function definition:
在我的 .h 库类和函数定义中：
class CAnyseeUSBTVControllerDlg : public CDialog
{
// Construction
public:
int InitCaptureDevice(void);
Any idea how to resolve it?
知道如何解决吗？
"Error 1 error C2375: 'CAnyseeUSBTVControllerDlg::InitCaptureDevice' : redefinition; different linkage c:\Program Files\toATS_DVS\anysee\anyseee30\anyseee30\anyseeUSBTVControllerDlg.cpp 122 anyseee30"
“错误 1 错误 C2375：'CANyseeUSBTVControllerDlg::InitCaptureDevice'：重新定义；不同的链接 c:\Program Files\toATS_DVS\anysee\anyseee30\anyseee30\anyseeUSBTVControllerDlg.cpp 122 anyseee30”
回答by Rod
You have to make sure you use the same declaration in your header file. Otherwise it is seen as different methods.
您必须确保在头文件中使用相同的声明。否则，它被视为不同的方法。
class CAnyseeUSBTVControllerDlg : public CDialog
{
// Construction
public:
int InitCaptureDevice(void);
DLLEXPORT int CaptureDevice(void);
回答by Yippie-Ki-Yay
You can have DLLEXPORTstated in .cppfile, but not in a header file (because otherwise compiler treats these functions as different ones).
您可以DLLEXPORT在.cpp文件中声明，但不能在头文件中声明（否则编译器会将这些函数视为不同的函数）。
Make your definition also DLLEXPORT.
也做出你的定义DLLEXPORT。
回答by Mark B
From http://tldp.org/HOWTO/C++-dlopen/thesolution.html
来自http://tldp.org/HOWTO/C++-dlopen/thesolution.html
C++ has a special keyword to declare a function with C bindings: extern "C". A function declared as extern "C" uses the function name as symbol name, just as a C function. For that reason, only non-member functions can be declared as extern "C", and they cannot be overloaded.
C++ 有一个特殊的关键字来声明一个带有 C 绑定的函数：extern "C"。声明为 extern "C" 的函数使用函数名作为符号名，就像 C 函数一样。因此，只能将非成员函数声明为 extern "C"，并且它们不能被重载。
I believe static members may also be possible to extern "C", but you can't do what you're trying to do directly. You'll need to make a C-only wrapper interface that calls your class member functions. You can then extern "C"the wrappers and expose that outside your DLL.
我相信静态成员也可以extern "C"，但你不能直接做你想做的事。您需要创建一个仅 C 语言的包装器接口来调用您的类成员函数。然后extern "C"，您可以使用包装器并将其暴露在您的 DLL 之外。
回答by Fernando Gonzalez Sanchez
This may happen because
这可能是因为
- You defined the prototype of a function in different places with
different visibility (
externvsstatic) - Same as above but
different name mangling (
extern "C"vsextern "C++") - Same as above but different dll export (
__declspec(dllimport)vs__declspec(dllexport)).
- 您在不同可见性（
externvsstatic）的不同地方定义了一个函数的原型 - 与上面相同但名称修改不同（
extern "C"vsextern "C++"） - 与上面相同，但不同的 dll 导出（
__declspec(dllimport)vs__declspec(dllexport)）。
To solve, enable /p for files to see how they are preprocessed (this has to be in a file by file basis, and will stop generating .obj for that file), look for a .i file with the result.
要解决此问题，请为文件启用 /p 以查看它们是如何预处理的（这必须以文件为基础，并且将停止为该文件生成 .obj），查找带有结果的 .i 文件。
Or using /displayincludes, or simply greping thru the code.
或者使用/displayincludes，或者简单地通过代码greping。
回答by Gary Stewart
//foo.h
#pragma once
#ifdef FOO_EXPORTS
#define FOO_API __declspec(dllexport)
#else
#define FOO_API __declspec(dllimport)
#endif
namespace foo
{
class Baz
{
public:
FOO_API static auto say_hello() -> void;
};
}
The key things, not so much the function names, or my use of the trailing return type, is that you put the name of the #defined __declspec in front of the function you want to export, much like you would a type.
关键不是函数名称，也不是我对尾随返回类型的使用，而是将#defined __declspec 的名称放在要导出的函数前面，就像放置类型一样。
You would also do the same in the function definition:
你也可以在函数定义中做同样的事情：
//foo.cpp
#include "foo.h"
namespace foo
{
FOO_API auto Baz::say_hello() -> void
{
do
{
MessageBox(nullptr, L"Seems to be working okay!", L"OK", MB_OK);
exit(1);
}
while (0);
}
}
The function implementation isn't important, just that you put FOO_API in front.
函数实现并不重要，只是你把 FOO_API 放在前面。
回答by Rika
Today I faced the same issue and for me, I had failed to include the type before my class. That is I had to change :
今天我遇到了同样的问题，对我来说，我没有在课前包含这个类型。那是我必须改变：
class Core
{
private:
py::object cls;
py::object obj;
py::object startFunc;
py::object startFuncAsync;
py::object stopFunc;
...
public:
...
};
to
到
class COREAPI Core
{
private:
py::object cls;
py::object obj;
py::object startFunc;
py::object startFuncAsync;
py::object stopFunc;
...
public:
...
};
