Distribution.Client.Win32SelfUpgrade

Windows inherited a design choice from DOS that while initially innocuous has rather unfortunate consequences. It maintains the invariant that every open file has a corresponding name on disk. One positive consequence of this is that an executable can always find its own executable file. The downside is that a program cannot be deleted or upgraded while it is running without hideous workarounds. This module implements one such hideous workaround.

The basic idea is:

• Move our own exe file to a new name

• Copy a new exe file to the previous name

• Run the new exe file, passing our own PID and new path

• Wait for the new process to start

• Close the new exe file

• Exit old process

Then in the new process:

• Inform the old process that we've started

• Wait for the old process to die

• Delete the old exe file

• Exit new process