    -----------------------------------------------------------------------------
    -- |
    -- Module      :  GHC.ExecutionStack
    -- Copyright   :  (c) The University of Glasgow 2013-2015
    -- License     :  see libraries/base/LICENSE
    --
    -- Maintainer  :  cvs-ghc@haskell.org
    -- Stability   :  internal
    -- Portability :  non-portable (GHC Extensions)
    --
    -- This is a module for efficient stack traces. This stack trace implementation
    -- is considered low overhead. Basic usage looks like this:
    --
    -- @
    -- import GHC.ExecutionStack
    --
    -- myFunction :: IO ()
    -- myFunction = do
    --      putStrLn =<< showStackTrace
    -- @
    --
    -- Your GHC must have been built with @libdw@ support for this to work.
    --
    -- @
    -- user@host:~$ ghc --info | grep libdw
    --  ,("RTS expects libdw","YES")
    -- @
    --
    -- @since 4.9.0.0
    -----------------------------------------------------------------------------

    module GHC.ExecutionStack (
        Location (..)
      , SrcLoc (..)
      , getStackTrace
      , showStackTrace
      ) where

    import Control.Monad (join)
    import GHC.ExecutionStack.Internal

    -- | Get a trace of the current execution stack state.
    --
    -- Returns @Nothing@ if stack trace support isn't available on host machine.
    getStackTrace :: IO (Maybe [Location])
    getStackTrace = (join . fmap stackFrames) `fmap` collectStackTrace

    -- | Get a string representation of the current execution stack state.
    showStackTrace :: IO (Maybe String)
    showStackTrace = fmap (\st -> showStackFrames st "") `fmap` getStackTrace