Global hook take effects when the API is called for the second time - dll

Question

All
I have implemented a global Windows hook to hook the API MessageBox(), the hook is implemented in a dll, when I setup the windows hook in a win32 console application (with the dll loaded) and call MessageBox(), the API is successfully hooked. For brevity, I name this win32 application EXE1.
Since I set up a global hook, I also want the calls to MessageBox() by other applications also be hooked. Therefore, I run another win32 console application -- EXE2 (with EXE1 running at the same time), which calls MessageBox() for three times. However, the first call is not hooked. I don't know why. (The code is in ansi format.) The codes are as follows:
-----------------------dll--------------------------------------------
#pragma once
#ifndef _WIN32_WINNT // Allow use of features specific to Windows XP or later.
#define _WIN32_WINNT 0x0501 // Change this to the appropriate value to target other versions of Windows.
#endif
//for the getaddrinfo test
#include <WS2tcpip.h>
#pragma comment(lib, "ws2_32")
#include <windows.h>
#include <stdio.h>
#include "mhook.h"
//=========================================================================
// Define _MessageBox so we can dynamically bind to the function
typedef int (WINAPI* _MessageBox) (HWND, LPCTSTR, LPCTSTR, UINT);
//=========================================================================
// Get the current (original) address to the functions to be hooked
//
_MessageBox TrueMessageBox = (_MessageBox)GetProcAddress(GetModuleHandle(L"user32"), "MessageBoxW");
//=========================================================================
// This is the function that will replace MessageBox once the hook
// is in place
MMRESULT WINAPI HookMessageBoxW(HWND hWnd, LPCTSTR lpText, LPCTSTR lpCaption, UINT uType){
printf("***** Call to MessageBox\n");
lpText = L"hooked MessageBox";
// Call the original waveInOpen function
MMRESULT nResult = TrueMessageBox(hWnd, lpText, lpCaption, uType);
return nResult;
}
///////////////////////////////////////////////////////////////////////////
#pragma comment(linker, "/SECTION:YCIShared,RWS")
#pragma data_seg("YCIShared")
HHOOK g_hHook = NULL;
#pragma data_seg()
HMODULE hInstance = 0;
static LRESULT WINAPI GetMsgProc(int code, WPARAM wParam, LPARAM lParam)
{ printf("=======\n");
//Mhook_SetHook((PVOID*)&TrueMessageBox, HookMessageBoxW);
return ::CallNextHookEx(g_hHook, code, wParam, lParam);
}
BOOL WINAPI SetSysHook(BOOL bInstall, DWORD dwThreadId)
{
BOOL bOk;
if(bInstall)
{
g_hHook = ::SetWindowsHookEx(WH_GETMESSAGE, GetMsgProc,
hInstance, dwThreadId);
bOk = (g_hHook != NULL);
}
else
{
bOk = ::UnhookWindowsHookEx(g_hHook);
g_hHook = NULL;
}
return bOk;
}
BOOL APIENTRY DllMain( HANDLE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
switch (ul_reason_for_call)
{
case DLL_PROCESS_ATTACH:
hInstance = (HINSTANCE) hModule;
printf("dll loaded!============================\n");
if(Mhook_SetHook((PVOID*)&TrueMessageBox, HookMessageBoxW)) //hook
printf("MessageBox Hook Succeeded!\n");
else
printf("MessageBox Hook Failed");
break;
case DLL_PROCESS_DETACH:
Mhook_Unhook((PVOID*)&TrueMessageBox);
break;
}
return TRUE;
}
-------------------------------end of dll---------------------------------------------
You cannot build this dll because it calls a self-implemented function Mhook_SetHook() and Mhook_Unhook(), which are from mhook. The DLL file is named as mhook-2.3-dll.dll.
------------------------------EXE1---------------------------------------------------
#pragma once
#ifndef _WIN32_WINNT // Allow use of features specific to Windows XP or later.
#define _WIN32_WINNT 0x0501 // Change this to the appropriate value to target other versions of Windows.
#endif
#include <windows.h>
#include <stdio.h>
#pragma comment(lib, "mhook-2.3-dll.lib")
extern "C" _declspec(dllimport) BOOL WINAPI SetSysHook(BOOL bInstall, DWORD dwThreadId);
int wmain(int argc, WCHAR* argv[])
{
//HMODULE hModule = ::LoadLibrary(L"mhook-2.3-dll.dll");
SetSysHook(TRUE, 0);
MessageBoxW(NULL, (LPCTSTR)L"MessageBox", NULL, MB_OK); //hooked
SetSysHook(FALSE, 0);
return 0;
}
--------------------------------end of EXE1-----------------------------------------
--------------------------------EXE2------------------------------------------------
#include
#include
int main(){
MessageBox(NULL, (LPCTSTR)L"MessageBox1", NULL, MB_OK); //not hooked
MessageBox(NULL, (LPCTSTR)L"MessageBox2", NULL, MB_OK); //hooked
MessageBox(NULL, (LPCTSTR)L"MessageBox3", NULL, MB_OK); //hooked
return 0;
}
-------------------------------end of EXE2------------------------------------------