------------------------------------------------------------------------------- |-- 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-----------------------------------------------------------------------------moduleGHC.ExecutionStack(Location (..),SrcLoc (..),getStackTrace ,showStackTrace )whereimportControl.Monad (join )importGHC.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 :: IO (Maybe [Location])
getStackTrace =(Maybe (Maybe [Location]) -> Maybe [Location]
forall (m :: * -> *) a. Monad m => m (m a) -> m a
join (Maybe (Maybe [Location]) -> Maybe [Location])
-> (Maybe StackTrace -> Maybe (Maybe [Location]))
-> Maybe StackTrace
-> Maybe [Location]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (StackTrace -> Maybe [Location])
-> Maybe StackTrace -> Maybe (Maybe [Location])
forall a b. (a -> b) -> Maybe a -> Maybe b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap StackTrace -> Maybe [Location]
stackFrames )(Maybe StackTrace -> Maybe [Location])
-> IO (Maybe StackTrace) -> IO (Maybe [Location])
forall a b. (a -> b) -> IO a -> IO b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
`fmap` IO (Maybe StackTrace)
collectStackTrace -- | Get a string representation of the current execution stack state.showStackTrace ::IO (Maybe String )showStackTrace :: IO (Maybe String)
showStackTrace =([Location] -> String) -> Maybe [Location] -> Maybe String
forall a b. (a -> b) -> Maybe a -> Maybe b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap (\[Location]
st ->[Location] -> ShowS
showStackFrames [Location]
st String
"")(Maybe [Location] -> Maybe String)
-> IO (Maybe [Location]) -> IO (Maybe String)
forall a b. (a -> b) -> IO a -> IO b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
`fmap` IO (Maybe [Location])
getStackTrace