#11944: Simplifier ticks exhausted When trying UnfoldingDone ip_X7RI -----------------------------------+-------------------------------------- Reporter: simone.trubian | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -----------------------------------+-------------------------------------- Description changed by simonpj: @@ -68,2 +68,3 @@ - - ```<no location info>: + We get + {{{ + <no location info>: @@ -77,2 +78,2 @@ - Total ticks: 53522k``` - + Total ticks: 53522k + }}} New description: When trying compiling the following code I get a ghc panic {{{#!hs import Network.Wai import Network.Wai.Handler.Warp import Network.HTTP.Types ( status200 , status404) import Blaze.ByteString.Builder (copyByteString) import qualified Data.ByteString.UTF8 as BU import Data.Monoid main = do let port = 3000 putStrLn $ "Listening on port " ++ show port run port app app req respond = respond $ case pathInfo req of ["avOK"] -> avOK ["avWrong"] -> avWrong x -> index x avOK = responseBuilder status200 [("Content-Type", "text/html")] $ mconcat $ map copyByteString [ "<!DOCTYPE html>" , "<html>" , "<head>" , "<title>Title</title>" , "</head>" , "<body>" , "<div class=\"status\">" , "In stock, usually dispatched in 1 business day" , "</div>" , "</body>" , "</html>"] avWrong = responseBuilder status404 [("Content-Type", "text/html")] $ mconcat $ map copyByteString ["<p>wong!</p>"] index x = responseBuilder status200 [("Content-Type", "text/html")] $ mconcat $ map copyByteString [ "<p>Hello from " , BU.fromString $ show x , "!</p>" , "<p><a href='/yay'>yay</a></p>\n" ] }}} We get {{{ <no location info>: ghc: panic! (the 'impossible' happened) (GHC version 7.10.2 for x86_64-unknown-linux): Simplifier ticks exhausted When trying UnfoldingDone ip_X7RI To increase the limit, use -fsimpl-tick-factor=N (default 100) If you need to do this, let GHC HQ know, and what factor you needed To see detailed counts use -ddump-simpl-stats Total ticks: 53522k }}} After a little bit of debugging I realised that it's the `copyBytestring` imported from `import Blaze.ByteString.Builder` function that is causing trouble, by reducing the number of elements in the list the function doesn't crash the compiler, so for instance: {{{#!hs avOK = responseBuilder status200 [("Content-Type", "text/html")] $ mconcat $ map copyByteString [ "<!DOCTYPE html>" , "<html><head><title>Title</title></head>" , "<body>" , "<div class=\"status\">" , "In stock, usually dispatched in 1 business day" , "</div>" , "</body>" , "</html>"] }}} compiles happily. I'm using - bytestring-0.10.6.0 - wai-3.0.4.0 - warp-3.1.8 - http-types-0.8.6 - blaze-builder-0.4.0.1 - utf8-string-1.0.1.1 -- -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11944#comment:1> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler