#7794: GHCi "Prelude.undefined" exceptions on ARM; ByteCodeItbls.mkJumpToAddr unimplemented -------------------------------+--------------------------- Reporter: cjwatson | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: GHCi | Version: 7.6.2 Resolution: | Keywords: Operating System: Linux | Architecture: arm Type of failure: GHCi crash | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------+--------------------------- Comment (by cjwatson): Replying to [comment:4 RoboTux]:

Inlining the call of the cacheflush system call (the call behind {{{__clear_cache}}}) should work but it means the cache would be flush every time mkJumpToAddr is called. I don't know enough the context of the code generation but if that function is called several time after 1 code generation then it's suboptimal.

It will be called every time one of the generated chunks of code is called, so I would expect it to be suboptimal, yes. That in itself might be tolerable. Much more importantly, though, this patch misses the point of flushing the instruction cache. The point is that we need to flush the cache in order for the processor to reliably read back the code that we just wrote out; flushing the cache in that very code is not a viable approach to that, because the cache-flushing code itself might not be read. So I'm afraid I don't think this is going to work properly. It might work some of the time, of course, depending on cache locality, but I can't see how it would work reliably. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7794#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler