#12562: GHC panic on rebuild (idInfo r_XsTP) -------------------------------------+------------------------------------- Reporter: cocreature | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- First of all let me apologize for the terrible testcase. I tried to find a smaller one (and am still trying) but haven’t managed to do so. The good news is that at least for me it’s reproducible === Steps to reproduce === {{{ git clone 'git@github.com:bscarlet/llvm-general.git' -b llvm-3.8 cd llvm-general cabal new-build llvm-general curl -s https://gist.githubusercontent.com/cocreature/c6807d7906756a2d58b8fe774141bf...
out.patch git apply out.patch cabal new-build llvm-general }}}
The patch just adds a newline somewhere to create a rebuild. I’ve seen this panic for completely different changes (all in this project) so I don’t think the change matters. I’ve also seen this panic with stack, cabal new-build and cabal build (using sandboxes). === Output === {{{ In order, the following will be built (use -v for more details): llvm-general-3.8.0.0 Preprocessing library llvm-general-3.8.0.0... [84 of 92] Compiling LLVM.General.Internal.Module ( src/LLVM/General/Internal/Module.hs, /home/moritz/tmp/llvm-general/dist- newstyle/build/llvm-general-3.8.0.0/build/LLVM/General/Internal/Module.o ) [85 of 92] Compiling LLVM.General.Module ( src/LLVM/General/Module.hs, /home/moritz/tmp/llvm-general/dist-newstyle/build/llvm- general-3.8.0.0/build/LLVM/General/Module.o ) [LLVM.General.Internal.Module changed] [89 of 92] Compiling LLVM.General.Internal.PassManager ( src/LLVM/General/Internal/PassManager.hs, /home/moritz/tmp/llvm-general /dist-newstyle/build/llvm- general-3.8.0.0/build/LLVM/General/Internal/PassManager.o ) [TH] ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): idInfo r_XsTP Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} === Comments === In this case this can be resolved by running cabal new-build again. However I’ve also had cases where this didn’t fix it and I had to blow away dist-newstyle. I haven’t yet managed to find a reproducible testcase for the latter. Matthew Pickering mentioned that he encountered this (or a similar) bug while building GHC. I tried core-lint but that didn’t help. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12562 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler