How do we tell if a C++ application is launched as a Windows service?

Question

We have a console app which we launch from command prompt for debugging, but we also launch this as an NT service for production.

Right now, the code has this logic:<

Answer 1

Here's some code I created (seems to work nicely). Apologies for missing headers, #defines, etc. If you want to see the full version, look here.

bool
CArchMiscWindows::wasLaunchedAsService() 
{
    CString name;
    if (!getParentProcessName(name)) {
        LOG((CLOG_ERR "cannot determine if process was launched as service"));
        return false;
    }

    return (name == SERVICE_LAUNCHER);
}

bool
CArchMiscWindows::getParentProcessName(CString &name) 
{   
    PROCESSENTRY32 parentEntry;
    if (!getParentProcessEntry(parentEntry)){
        LOG((CLOG_ERR "could not get entry for parent process"));
        return false;
    }

    name = parentEntry.szExeFile;
    return true;
}

BOOL WINAPI 
CArchMiscWindows::getSelfProcessEntry(PROCESSENTRY32& entry)
{
    // get entry from current PID
    return getProcessEntry(entry, GetCurrentProcessId());
}

BOOL WINAPI 
CArchMiscWindows::getParentProcessEntry(PROCESSENTRY32& entry)
{
    // get the current process, so we can get parent PID
    PROCESSENTRY32 selfEntry;
    if (!getSelfProcessEntry(selfEntry)) {
        return FALSE;
    }

    // get entry from parent PID
    return getProcessEntry(entry, selfEntry.th32ParentProcessID);
}

BOOL WINAPI 
CArchMiscWindows::getProcessEntry(PROCESSENTRY32& entry, DWORD processID)
{
    // first we need to take a snapshot of the running processes
    HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
    if (snapshot == INVALID_HANDLE_VALUE) {
        LOG((CLOG_ERR "could not get process snapshot (error: %i)", 
            GetLastError()));
        return FALSE;
    }

    entry.dwSize = sizeof(PROCESSENTRY32);

    // get the first process, and if we can't do that then it's 
    // unlikely we can go any further
    BOOL gotEntry = Process32First(snapshot, &entry);
    if (!gotEntry) {
        LOG((CLOG_ERR "could not get first process entry (error: %i)", 
            GetLastError()));
        return FALSE;
    }

    while(gotEntry) {

        if (entry.th32ProcessID == processID) {
            // found current process
            return TRUE;
        }

        // now move on to the next entry (when we reach end, loop will stop)
        gotEntry = Process32Next(snapshot, &entry);
    }

return FALSE;

}