GhcEventsAnalyze.hs

{-# LANGUAGE GHC2021 #-}

-- | This module emits events in the eventlog which can then be analyzed with
-- [ghc-events-analyze](https://hackage.haskell.org/package/ghc-events-analyze).
--
-- TLDR:
--
-- * Compile with @$ ghc -eventlog@
-- * Run the program as @$ myprogram +RTS -l@
-- * Observe the produced event log with @$ ghc-events-analyze \<log\>@
module Benign.GhcEventsAnalyze where

import Benign qualified
import Debug.Trace (traceEventIO)

-- | @'event' name strat thing@ emits a @"START " ++ name@ event before
-- evaluating @strat thing@. And a @"END " ++ name@ event when the evaluation is
-- complete. See also 'Debug.Trace.traceEvent'.
event :: String -> Benign.Strat a -> a -> a
event event_name =
  Benign.unsafeSpanBenign
    (traceEventIO $ "START " ++ event_name)
    (traceEventIO $ "STOP " ++ event_name)