C and C++ library error [duplicate] - c++

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"undefined reference to" errors when linking static C library with C++ code
(1 answer)
Closed 6 years ago.
I got 3 files (selfdelxp.c, selfdelxp.h and main.cpp)
selfdelxp.c was copied from http://blogorama.nerdworks.in/selfdeletingexecutables/ and I removed the main function as I try to use the SelfDelete() function in main.cpp
The problem comes when I try to compile it throwing the error undefined reference to 'SelfDelete()'
How can I make it work? What am I doing wrong? What I'm trying to do is to be able to use that function (SelfDelete()) in a program written in main.cpp
selfdelxp.c
//
// Self-deleting exe under Windows XP
//
#include <windows.h>
#include <tchar.h>
// get this right!
#define EXPLORER_PID 1444
typedef UINT (WINAPI * WAIT_PROC)(HANDLE, DWORD); // WaitForSingleObject
typedef BOOL (WINAPI * CLOSE_PROC)(HANDLE); // CloseHandle
typedef BOOL (WINAPI * DELETE_PROC)(LPCTSTR); // DeleteFile
typedef VOID (WINAPI * EXIT_PROC)(DWORD); // ExitProcess
typedef struct
{
WAIT_PROC fnWaitForSingleObject;
CLOSE_PROC fnCloseHandle;
DELETE_PROC fnDeleteFile;
EXIT_PROC fnExitProcess;
HANDLE hProcess;
TCHAR szFileName[MAX_PATH];
} INJECT;
#pragma optimize("gsy", off)
#pragma check_stack(off) // doesn't work :-(
DWORD WINAPI RemoteThread(INJECT *remote)
{
remote->fnWaitForSingleObject(remote->hProcess, INFINITE);
remote->fnCloseHandle(remote->hProcess);
remote->fnDeleteFile(remote->szFileName);
remote->fnExitProcess(0);
return 0;
}
#pragma check_stack
HANDLE GetRemoteProcess()
{
STARTUPINFO si = { sizeof(si) };
PROCESS_INFORMATION pi;
//return OpenProcess(PROCESS_ALL_ACCESS, FALSE, EXPLORER_PID);
if(CreateProcess(0, "explorer.exe", 0, 0, FALSE, CREATE_SUSPENDED|CREATE_NO_WINDOW|IDLE_PRIORITY_CLASS, 0, 0, &si, &pi))
{
CloseHandle(pi.hThread);
return pi.hProcess;
}
else
{
return 0;
}
}
PVOID GetFunctionAddr(PVOID func)
{
#ifdef _DEBUG
// get address of function from the JMP <relative> instruction
DWORD *offset = (BYTE *)func + 1;
return (PVOID)(*offset + (BYTE *)func + 5);
#else
return func;
#endif
}
BOOL SelfDelete()
{
INJECT local, *remote;
BYTE *code;
HMODULE hKernel32;
HANDLE hRemoteProcess;
HANDLE hCurProc;
DWORD dwThreadId;
HANDLE hThread = 0;
char ach[80];
hRemoteProcess = GetRemoteProcess();
if(hRemoteProcess == 0)
return FALSE;
// Allocate memory in remote process
code = VirtualAllocEx(hRemoteProcess, 0, sizeof(INJECT) + 128, MEM_RESERVE|MEM_COMMIT, PAGE_EXECUTE_READWRITE);
if(code == 0)
{
CloseHandle(hRemoteProcess);
return FALSE;
}
hKernel32 = GetModuleHandle(_T("kernel32.dll"));
// setup remote structure
remote = (INJECT *)(code + 128);
local.fnWaitForSingleObject = (WAIT_PROC)GetProcAddress(hKernel32, "WaitForSingleObject");
local.fnCloseHandle = (CLOSE_PROC)GetProcAddress(hKernel32, "CloseHandle");
local.fnExitProcess = (EXIT_PROC)GetProcAddress(hKernel32, "ExitProcess");
#ifdef UNICODE
local.fnDeleteFile = (DELETE_PROC)GetProcAddress(hKernel32, "DeleteFileW");
#else
local.fnDeleteFile = (DELETE_PROC)GetProcAddress(hKernel32, "DeleteFileA");
#endif
// duplicate our own process handle for remote process to wait on
hCurProc = GetCurrentProcess();
DuplicateHandle(hCurProc, hCurProc, hRemoteProcess, &local.hProcess, 0, FALSE, DUPLICATE_SAME_ACCESS);
// find name of current executable
GetModuleFileName(NULL, local.szFileName, MAX_PATH);
// write in code to execute, and the remote structure
WriteProcessMemory(hRemoteProcess, code, GetFunctionAddr(RemoteThread), 128, 0);
WriteProcessMemory(hRemoteProcess, remote, &local, sizeof(local), 0);
wsprintf(ach, "%x %x\n", code, remote);
OutputDebugString(ach);
// execute the code in remote process
hThread = CreateRemoteThread(hRemoteProcess, 0, 0, code, remote, 0, &dwThreadId);
if(hThread != 0)
{
CloseHandle(hThread);
}
return TRUE;
}
/*int main(void)
{
SelfDelete();
return 0;
}*/
selfdelxp.h
#ifndef SELFDELETE_H_
#define SELFDELETE_H_
#include <stdbool.h>
bool SelfDelete(void);
#endif // SELFDELETE_H_
main.cpp
#include <iostream>
#include "selfdelxp.h"
using namespace std;
int main()
{
SelfDelete();
return 0;
}

Answer 1

You're getting caught out by C++ name mangling. Note selfdelxp.c is presumably compiled as C code. You need to add extern "C" { ... } around the SelfDelete() deceleration or try compiled selfdelxp.c as cpp (e.g. rename it).
Here is how you would do it with the first approach.
#include <windows.h>
extern "C" {
BOOL SelfDelete();
}
(You could also declare that using C++ bool and probably be okay but afik it is better to include windows.h and use the same type)