id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,difficulty,testcase,blockedby,blocking,related
2650,Child processes always unwantedly inherit Handles on Windows,Deewiant,simonmar,"`runInteractiveProcess` (the one in `runProcess.c`, not the Haskell one) calls `CreateProcess` with `bInheritHandles` set to `TRUE`, but the whole thing is not wrapped in a critical section. Microsoft has [http://support.microsoft.com/kb/315939 a decent explanation of why this is a problem] and I found that it's [http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6428742 a two-year old unfixed bug in the Java runtime] as well.

In case it's not obvious, the reason why we don't want Handles to be inherited is that then a child process may hang on to it well after it should have been closed. The end result is that trying to do anything to it results in a sharing violation. The case in which I originally ran into this was `System.Directory.copyFile` intermittently reporting a ""permission denied"" error for a temp file it was using. I think it was trying to delete it, but failing because a child process somewhere was hanging on to the Handle.

Attached is code demonstrating the problem. It forks a thread which repeatedly tries to open and close the file `foo.tmp`. The main thread then spawns processes as fast as it can until the other one fails to open the file. This, I think, cannot happen on non-Windows platforms since two processes can have the same file open without trouble. '''Do not run except on Windows, you risk flooding your system with `ping` processes.'''

It may be sensible to make this controllable with the `close_fds` parameter to `createProcess`, which is currently just ignored on Windows. I can't see why anybody could ever want this behaviour, though.

I've tested only process-1.0.1 with it, and the `openFile` fails reliably after spawning up to about 4 processes.",bug,closed,high,6.12.1,libraries/process,6.9,fixed,,ndmitchell@…,Windows,Unknown/Multiple,,Unknown,,,,