On FreeBSD using ghc 4.04, long running commands executed with
System.system are being interrupted by virtual alarms leading to
errors such as:
o Fail: interrupted
Action: system
Reason: system command interrupted rm -f xxx yyy
o Virtual timer expired
o gcc: Internal compiler error: program cpp got fatal signal 26
(Depending on which command was interrupted.)
After looking at ghc 4.02's libraries for a while (it's all I had
around), it looks as though ghc-4.02/ghc/lib/std/cbits/system.c should
mask the SIGVTALRM signal after executing fork and before executing
exec*. (Obviously it should also mask any other signals not set by
the users code.)
[Incidentally, I'm not sure why this SIGVTALRM is enabled though since
the online documentation for -C says that context switches happen on
heap checks not on timeouts.]
A workaround for now is to use this:
System.system ("trap '' 26; " ++ xs)
instead of
System.system xs
though you could be really unlucky and get a signal before the trap
is disabled.
--
Alastair Reid
ps I'm guessing that problem has been in the code ever since it was
written - wonder why it's never hit anyone before?
