#15038: Memory Corruption (strange closure type) -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.6.1 Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): Replying to [comment:19 osa1]:
STG for `absentError`: ...
Apparently this is CAFFY (othewise we'd see `Caf=NoCafRefs`).
I also realized that unarise uses `absentError` wrong: `absentError` expects an `Addr#` argument (for a string that represents the "absent" argument) but unarise just uses `absentError` without an argument. So
Right, that's what I suspected. there's also a type error.
Applying `absentError` to an argument in unarise would mean let bindings (heap allocation) so perhaps we should use something else for unused
Yikes! It seems like this is one case that the old STG lint type-checker likely could have caught. Oh well. pointer location in unboxed sums. (IIRC when we first used `absentError` it wasn't taking an argument)
If the id we'll use instead of `absentError` is not CAFFY then this
problem will disappear. Yes, this seems like the shortest path to solving this. Introduce a variant of `absentError` that throws a less helpful error message but requires no allocation and isn't caffy.
However I wonder if we could somehow implement a check that ensures we won't make things more caffy after `TidyPgm` in the future.
The whole interaction between CorePrep, CoreTidy, and caffyness is quite unfortunate. It would be better if CorePrep and CoreTidy were less coupled in this regard. I thought there was a ticket discussing this, but I'm having trouble finding it at the moment. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15038#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler