【问题标题】：Already defined in *.obj已经在 *.obj 中定义
【发布时间】：2014-11-02 03:17:05
【问题描述】：

我正在做一些函数来帮助制作钩子。我想将这些函数保留在一个文件中，并在需要时包含它。

我不知道它是否还在工作，但这不是问题。当我编译时，我得到这个错误。我认为导入是错误的。

错误：

1>noxHook.obj : error LNK2005: "unsigned long tpAddr" (?tpAddr@@3KA) already defined in Hook.obj
1>noxHook.obj : error LNK2005: "void __cdecl StopHook(struct cHook)" (?StopHook@@YAXUcHook@@@Z) already defined in Hook.obj
1>noxHook.obj : error LNK2005: "void __cdecl StartHook(struct cHook)" (?StartHook@@YAXUcHook@@@Z) already defined in Hook.obj
1>noxHook.obj : error LNK2005: "struct cHook __cdecl SetupHook(unsigned long,void *,void * *)" (?SetupHook@@YA?AUcHook@@KPAXPAPAX@Z) already defined in Hook.obj
1>noxHook.obj : error LNK2005: "void __cdecl tpHook(void)" (?tpHook@@YAXXZ) already defined in Hook.obj
1>C:\Users\JorgeFranzon\Documents\Visual Studio 2008\Projects\Hook\Release\Hook.dll : fatal error LNK1169: one or more multiply defined symbols found

钩子.cpp：

#include "noxHook.cpp"


int(*tFunc)(int a, int b) = NULL;

int hkFunc(int a, int b)
{
    printf("\n      Hook: Original parameters: %d and %d\n", a, b);
    return tFunc(98, 99);
}

void Main()
{
    struct cHook hk1 = SetupHook(0x4016B0, hkFunc, &(PVOID&)tFunc);
    StartHook(hk1);
}

BOOL APIENTRY DllMain(HANDLE hModule, DWORD dwReason, LPVOID lpReserved)
{
    switch (dwReason)
    {
    case DLL_PROCESS_ATTACH:
        Main();
        break;
    }
    return TRUE;
}

noxHook.cpp：

#include <windows.h>
#include <stdio.h>

#define Naked __declspec( naked )

extern DWORD tpAddr = 0;

struct cHook
{
    BYTE newBytes[6];;
    BYTE oldBytes[6];
    DWORD fromAddr;
    LPVOID toAddr;
};

Naked void tpHook()
{
    __asm NOP;
    __asm NOP;
    __asm NOP;
    __asm NOP;
    __asm NOP;
    __asm NOP;

    __asm PUSH tpAddr;
    __asm RET;
}

struct cHook SetupHook(DWORD fromAddr, LPVOID toAddr, LPVOID *oAddr)
{
    struct cHook tmpHook;
    tmpHook.fromAddr = fromAddr;
    tmpHook.toAddr = toAddr;

    DWORD oldProt;
    VirtualProtect((void*)fromAddr, 6, PAGE_EXECUTE_READWRITE, &oldProt);

    tmpHook.newBytes[0] = 0x68;
    memcpy(&tmpHook.newBytes[1], &toAddr, 4);
    tmpHook.newBytes[5] = 0xC3;

    memcpy(&tmpHook.oldBytes[0], &fromAddr, 6);

    tpAddr = fromAddr + 6;
    memcpy(&tpHook, &tmpHook.oldBytes[0], 6);

    *oAddr = tpHook;


    return tmpHook;
}

void StartHook(struct cHook tmpHook)
{
    memcpy((void*)tmpHook.fromAddr, (void*)&tmpHook.newBytes, 6);
}

void StopHook(struct cHook tmpHook)
{
    memcpy((void*)tmpHook.fromAddr, tmpHook.oldBytes, 6);
}

【问题讨论】：

你为什么要#include一个.cpp文件？
将声明放入.hpp 文件，然后将#include 放入它们并链接到从您的.cpps 创建的.o 文件
通常包含的文件是.h、.hpp 或类似（头文件）。包括.cpp 在大多数情况下是不必要的。函数的定义放在.hpp中，实现放在.cpp中，如果全局变量在多个.cpp中使用，则在一个中声明，在另一个中添加extern链接。
我将 noxHook.cpp 重命名为 noxHook.h 和 0 个错误！
在头文件中包含大量的实现细节几乎总是一个坏主意。最好将接口与实现分开；单独编译是有原因的。

标签： c++ c windows visual-c++ assembly

【解决方案1】：

为了更好的理解：

您很可能会遇到多定义错误，因为您既 #includeing 又链接同一个文件。

解决此问题的标准方法是拆分您的接口和实现，将声明放置在您 #include 的受保护头文件中，并将定义放入 @ 987654323@ 编译和链接的文件。

对于您的示例，这可能如下所示：

钩子.cpp

#include "noxHook.hpp"


int(*tFunc)(int a, int b) = NULL;

int hkFunc(int a, int b)
{
    printf("\n      Hook: Original parameters: %d and %d\n", a, b);
    return tFunc(98, 99);
}

void Main()
{
    struct cHook hk1 = SetupHook(0x4016B0, hkFunc, &(PVOID&)tFunc);
    StartHook(hk1);
}

BOOL APIENTRY DllMain(HANDLE hModule, DWORD dwReason, LPVOID lpReserved)
{
    switch (dwReason)
    {
    case DLL_PROCESS_ATTACH:
        Main();
        break;
    }
    return TRUE;
}

noxHook.cpp

#include <stdio.h>
#include "noxHook.hpp"

extern DWORD tpAddr = 0;

Naked void tpHook()
{
    __asm NOP;
    __asm NOP;
    __asm NOP;
    __asm NOP;
    __asm NOP;
    __asm NOP;

    __asm PUSH tpAddr;
    __asm RET;
}

struct cHook SetupHook(DWORD fromAddr, LPVOID toAddr, LPVOID *oAddr)
{
    struct cHook tmpHook;
    tmpHook.fromAddr = fromAddr;
    tmpHook.toAddr = toAddr;

    DWORD oldProt;
    VirtualProtect((void*)fromAddr, 6, PAGE_EXECUTE_READWRITE, &oldProt);

    tmpHook.newBytes[0] = 0x68;
    memcpy(&tmpHook.newBytes[1], &toAddr, 4);
    tmpHook.newBytes[5] = 0xC3;

    memcpy(&tmpHook.oldBytes[0], &fromAddr, 6);

    tpAddr = fromAddr + 6;
    memcpy(&tpHook, &tmpHook.oldBytes[0], 6);

    *oAddr = tpHook;


    return tmpHook;
}

void StartHook(struct cHook tmpHook)
{
    memcpy((void*)tmpHook.fromAddr, (void*)&tmpHook.newBytes, 6);
}

void StopHook(struct cHook tmpHook)
{
    memcpy((void*)tmpHook.fromAddr, tmpHook.oldBytes, 6);
}

noxHook.hpp

#include <windows.h>

#define Naked __declspec( naked )

struct cHook
{
    BYTE newBytes[6];;
    BYTE oldBytes[6];
    DWORD fromAddr;
    LPVOID toAddr;
};

Naked void tpHook();
struct cHook SetupHook(DWORD fromAddr, LPVOID toAddr, LPVOID *oAddr);
void StartHook(struct cHook tmpHook);
void StopHook(struct cHook tmpHook);

【讨论】：