#9168: reading/writing blocking FDs over FD_SETSIZE is broken ------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.8.1 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- In `GHC.IO.FD` when reading from or writing to a blocking FD we first check (using our C function `fdReady`) whether the underlying fd is ready for read/write, in an attempt to avoid blocking the current OS thread. On POSIX this check is done using select, with no test for whether the fd exceeds `FD_SETSIZE`, causing a write out of bounds and various bad consequences. Also, while `readRawBufferPtr` checks the error status of `fdReady`, `readRawBufferPtrNoBlock`, `writeRawBufferPtr`, `writeRawBufferPtrNoBlock` do not, making this issue harder to diagnose. I suggest that `fdReady` use `poll(2)` where available. I can prepare a set of patches if needed. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9168 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler