QProcess::startDetached blocked by UAC (running an updater)

I have an update function in my app - it downloads and verifies the installer (a setup.exe, created with NSIS). To actually kick off the update, I have simply been doing:

QString path = .. absolute path to the downloaded file ...
QProcess::startDetached(path, QStringList());

This works fine on XP - but on Vista and Win7, nothing happens once the download completes. If I browse to the downloaded update and run it manually, it works fine. I assume what's happening is that UAC is blocking the installer at CreateProcess time, but this is where my knowledge runs out.

Additional complication - when I'm running a debug build from the command line, the steps above work - I get the UAC prompt and can run the installer. It's the release builds, started form the start menu/shortcut, which have the issue - I assume there's a difference in the开发者_开发知识库 auth token when running from a command shell.

You can also use

QDesktopServices::openUrl(QUrl::fromLocalFile(path));

Might be surprising and counterintuitive, but it works and is more cross-platform

If you are not admin and you call CreateProcess() on a .exe with a "Vista" manifest (or no manifest, but a .exe that windows detects as an installer (This includes NSIS)) the call fails, you need to use ShellExecute[Ex](). ShellExecute will trigger UAC prompt if required...

This seems to be a Qt bug, see QTBUG-9761 , the correct workaround is to use ShellExecute with lpOperation set to runas.

Another alternative is to prepend your execution with cmd.exe /C. This effectively routes your execution through the shell, so you do get the UAC prompt. The downside is that if your process fails you probably won't get as much information had you gone through ShellExecute[Ex], but on the plus side you will get all the facilities of QProcess that you miss if you use QDesktopServices::openUrl, where you have no idea if things worked or not.