#291: cabal-install cannot re-install itself on windows ---------------------------------+------------------------------------------ Reporter: duncan | Owner: Type: defect | Status: new Priority: normal | Milestone: Component: cabal-install tool | Version: 1.2.3.0 Severity: normal | Resolution: Keywords: | Difficulty: normal Ghcversion: 6.8.2 | Platform: Windows ---------------------------------+------------------------------------------ Comment (by duncan): See http://www.catch22.net/tuts/selfdel.asp for a menu of cunning trickery. Apparently one cannot open an .exe file with `FILE_FLAG_DELETE_ON_CLOSE` however one can execute an .exe file which is already open with `FILE_FLAG_DELETE_ON_CLOSE`. This is the basis of one of the tricks: {{{ [ Current process ] 1. Create a new file with FILE_FLAG_DELETE_ON_CLOSE. 2. Copy the current executable's content into the new file. 3. Create a new process with the duplicate executable: 4. Pass the current executable's full path and PID in the call to CreateFile. 5. Sleep for a short time to give the new process time to start. 6. Close the new file. 7. Exit current process. [ Duplicate process ] 8. Wait for the process specified on command-line to die. 9. Delete file specified on command-line. 10. Exit duplicate process. }}} A problem with implementing this one is getting the synchronisation right. Waiting for the new process to start requires synchronisation. We could do it by waiting for some time and hoping. Doing it properly needs some kind of cross-process lock like a mutex or something hacky like using a file as a lock. Waiting for the old process to die can be done, though not easily. The portable `System.Process` lets us wait for a process, but converting a pid into a ProcessHandle would be tricky (internally the types are incompatible, `type CPid = Word32` vs `type HANDLE = Ptr ()`). It might be more appealing to just leave the old file in place and delete it next time round. -- Ticket URL: http://hackage.haskell.org/trac/hackage/ticket/291#comment:3 Hackage http://haskell.org/cabal/ Hackage: Cabal and related projects