Global WH_CBT hook DLL is loaded into some processes only

The main program calls the function SetHook in the wi.dll to install global WH_CBT hook.

bool WI_API SetHook()
{
    if (!g_hHook)
    {
        g_hHook = SetWindowsHookEx(WH_CBT, (HOOKPROC) CBTProc, g_hInstDll, 0);
    }

    return g_hHook != NULL;
}

I presume after installing global hook, wi.dll should be loaded into each process' address space. However wi.dll is loaded in to some processes only. For example, if I start Skype, MS Word I can see that wi.dll is loaded into these processes as well (using Process Explorer), however if I run Firefox, uTorrent, Adobe Reader then wi.dll is not l开发者_JS百科oaded into these processes.

I'm using W7 64-bit, main program and wi.dll is 32-bit, all programs mentioned here is 32-bit programs as well.

Any ideas why that happens?

Thanks in advance.

From MSDN:

SetWindowsHookEx can be used to inject a DLL into another process. A 32-bit DLL cannot be injected into a 64-bit process, and a 64-bit DLL cannot be injected into a 32-bit process. If an application requires the use of hooks in other processes, it is required that a 32-bit application call SetWindowsHookEx to inject a 32-bit DLL into 32-bit processes, and a 64-bit application call SetWindowsHookEx to inject a 64-bit DLL into 64-bit processes. The 32-bit and 64-bit DLLs must have different names.

So, you should create 32-bit app to call SetWindowsHookEx from a 32-bit dll, then redirect the messages to your main app, and have your main app in x64 call SetWindowsHookEx from a 64-bit dll to receive messages from x64 processes as well.

The hook chain mechanism is not bulletproof and relies on everyone involved following the rules. If an application installs its own per-thread WH_CBT hook and does not call CallNextHookEx in its hook procedure, earlier hooks won't get called. See the MSDN docs for CallNextHookEx.