#13645: whoCreated produces an uninformative stack trace when an exception is raised in a CAF -------------------------------------+------------------------------------- Reporter: refold | Owner: (none) 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: -------------------------------------+------------------------------------- Consider the following program: {{{#!hs {-# LANGUAGE ScopedTypeVariables #-} module Main where import Control.Exception import GHC.Stack {-# NOINLINE caf #-} caf :: [Int] caf = [1..500] {-# NOINLINE caf_exc #-} caf_exc :: Int caf_exc = caf !! 1000 {-# NOINLINE foo #-} foo :: Int -> Int foo 0 = caf_exc foo n = foo $ n - 1 {-# NOINLINE bar #-} bar :: Int -> Int bar n = bar' n where bar' 0 = foo n bar' m = bar' $ m - 1 main :: IO () main = print (bar 10) `catch` \(e :: SomeException) -> do stacktrace <- whoCreated e print stacktrace }}} By default, when built with profiling, `whoCreated` in the example above produces a quite uninformative stack trace: {{{#!shell $ ./caf-nostack ["GHC.List.CAF (<entire-module>)"] }}} However, if you run the program with `+RTS -xc`, you'll see that it prints a stack trace with much more context: {{{#!shell $ ./caf-nostack +RTS -xc *** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: GHC.List.CAF --> evaluated by: Main.caf_exc, called from Main.CAF --> evaluated by: Main.foo, called from Main.bar.bar', called from Main.bar, called from Main.main, called from Main.CAF --> evaluated by: Main.main ["GHC.List.CAF (<entire-module>)"] }}} It'd be nice if `whoCreated` produced something closer to the `+RTS -xc` output in this case. Cabalised test project: https://github.com/23Skidoo/caf-nostack -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13645 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler