The zlib library internally uses a bunch of unsafe functions (`unsafePerformIO`, `unsafeForeignPtrToPtr`) so this is also quite
#9494: Probable data corruption with GHCi 7.8.* and Zlib -------------------------------------+------------------------------------- Reporter: nominolo | Owner: aseipp Type: bug | Status: new Priority: high | Milestone: Component: GHCi | Version: 7.8.3 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: Incorrect | Blocked By: result at runtime | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by nominolo): Replying to [comment:3 rwbarton]: possibly just a bug in zlib. (See `Codec/Compression/Zlib/Stream.hsc`, it's quite scary.) Yes, it's possible. I looked through that module, but could find any use of the Really Scary `inlinePerformIO`. The scariest functions seem to be `push{Input,Output}Buffer`. Unless we know what really goes wrong, it's possible that other libraries have the same problem and may break in subtle ways on 7.8 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9494#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler