[Solution] QProcess::startDetached cannot start process that requires elevated privileges in Microsoft Windows Vista, Windows Server 2008 or Windows 7

When running under Microsoft Windows Vista, Windows Server 2008 or Windows 7 with User Account Control (UAC) enabled, the following code always fails if starting a program that requires elevated privileges (it can be, for example, a setup program):

    QString exeFileName;

    /.../

    if (!QProcess::startDetached(exeFileName))
    {
        // error handling
    }

The inner reason for this failure is that QProcess::startDetached method under Windows internally calls CreateProcess function. CreateProcess called from a non-elevated process fails with ERROR_ELEVATION_REQUIRED if it tries to start an executable that requires elevation.

Corresponding error report in Qt Bug Tracker was rejected because it "sounds like a reasonable limitation of QProcess".

Below is a possible solution for this problem. In short: QProcess::startDetached is replaced with ShellExecute function.

#ifdef Q_OS_WIN
    #include <windows.h>
    #include <shellapi.h>
#endif

    /.../

    QString exeFileName;

    /.../


#ifdef Q_OS_WIN
    int result = (int)::ShellExecuteA(0, "open", exeFileName.toUtf8().constData(), 0, 0, SW_SHOWNORMAL);
    if (SE_ERR_ACCESSDENIED == result)
    {
        // Requesting elevation
        result = (int)::ShellExecuteA(0, "runas", exeFileName.toUtf8().constData(), 0, 0, SW_SHOWNORMAL);
    }
    if (result <= 32)
    {
        // error handling
    }
#else
    if (!QProcess::startDetached(exeFileName))
    {
        // error handling
    }
#endif