Hello fellow DWARF enthusiasts, Tonight I finally made something of a breakthrough on the DWARF front; after finding a small logic error in one of my patches I was able to get a full stack trace into and out of Haskell using the runtime system's native stack unwinder. This is quite exciting! Recall that up until now there have been a few issues which can lead to problems with unwinding, * #11353: Unsafe foreign calls can require the NCG to make stack pointer adjustments to accomodate native calling conventions. These adjustments need to be taken into account when we generate unwinding information. * #11337: Stack fixups produced by CmmStackLayout aren't reflected in unwinding information. Essentially this was a result of the fact that our current unwinding implementation assumes that stack layout is fixed over the course of a block. * #11338: The region surrounding safe foreign calls doesn't get proper unwinding information. I've solved all three of these in my branch, which I've rebased, split up, and posted to Phabricator. The result is quite a stack of differentials, * D2740: OrdList: Add Foldable, Traversable instances Some throat-clearing. * D2735: Use newBlockId instead of newLabelC Just some refactoring. * D2737: NCGMonad: Add MonadUnique NatM instance This will come in handy later. * D2736: AsmCodeGen: Refactor worker in cmmNativeGens More refactoring I did while trying to understand the dataflow in the NCG. * D2739: CmmCommonBlockElim: Ignore CmmUnwind nodes This is a fix to what I believe is a bug which I noticed while reading through the implementation. * D2741: Generalize CmmUnwind and pass unwind information through NCG This is the bulk of the change. Here we refactor the treatment of unwinding information to provide the flexibility we will need to address the issues described above and fix #11353. Review is badly needed here. * D2742: CmmLayoutStack: Add unwind information on stack fixups Here we use the infrastructure provided in D2741 to fix #11337. * D2743: StgCmmForeign: Emit debug information for safe foreign calls Here we fix #11338 by adding unwind information to the safe foreign call prologue/epilogue code. * D2738: Cmm: Add support for undefined unwinding statements Fix unwinding information for stg_stack_underflow_frames, which we have no means of unwinding out of. For this we need to add support for unwinding declarations which tell the underwinder to "forget" about the value of a register. Reviews would be greatly appreciated. Cheers, - Ben