#8281: The impossible happened: primRepToFFIType -------------------------------------+------------------------------------- Reporter: tibbe | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler | Version: 7.6.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonmar): @bgamari I understand the concerns and I agree. To answer your question about the rationale, the idea is that "safe" is the default and "unsafe" relaxes the compiler's obligations only. It doesn't add new obligations (such as the requirement not to interrupt the call with a GC). Implementing that obligation in GHCi might be possible, but we haven't done it. One way around this would be to add a new annotation to foreign calls that requires the call not to be interrupted by GC, e.g. `foreign import unsafenogc ...` or something. This would not be implemented by GHCi (yet?) so compilation would fail if you tried to load text into GHCi. Incidentally it's a bad idea to make one of these calls that might run for an arbitrarily long time, because if a GC strikes everything is blocked until the call returns. This has been a rich source of performance bugs in our system at Facebook. I don't think we've encountered problems with text, but we've had to fix other libraries (e.g. regex-pcre) to turn unsafe calls into safe calls. It's possible that the unsafe calls in Text would cause problems when working with very long strings. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8281#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler