Mute all errors from GC finite state machine assumption failures

unless assertions are turned on. This is to avoid any future
breakages due to wrong events order, as in #35 (and probably in #46).
For any events where the order is indeed wrong, the TS GC stats for
that particular GC are more ore less inaccurate. This probably doesn't
happen if the eventlogs are collected on an OS with a good resolution
of a time source (e.g., on modern Linux).

Author: Mikolaj

GUI/SummaryView.hs

@@ -687,6 +687,10 @@ emptyGenStat = GenStat
   , gcMaxPause = 0
   }
 
+-- Fail only when assertions are turned on.
+errorAs :: String -> a -> a
+errorAs msg a = assert (error msg) a
+
 accumEvent :: StatsAccum -> CapEvent -> StatsAccum
 accumEvent !statsAccum (CapEvent mcap ev) =
   let -- For events that contain a counter with a running sum.
@@ -775,8 +779,8 @@ accumEvent !statsAccum (CapEvent mcap ev) =
                   ModeEnd  -> dGC { gcMode = ModeIdle }
                   ModeIdle -> dGC
                   -- Impossible.
-                  ModeInit   -> error "scanEvents: GlobalSyncGC ModeInit"
-                  ModeSync{} -> error "scanEvents: GlobalSyncGC ModeSync"
+                  ModeInit   -> errorAs "scanEvents: GlobalSyncGC ModeInit" dGC
+                  ModeSync{} -> errorAs "scanEvents: GlobalSyncGC ModeSync" dGC
                   ModeGHC{}  -> -- error "scanEvents: GlobalSyncGC ModeGHC"
                                 dGC  -- workaround for #46
           GCStatsGHC{..} ->
@@ -838,7 +842,7 @@ accumEvent !statsAccum (CapEvent mcap ev) =
                   -- Cap not in the current GC, leave it alone.
                   ModeIdle -> dGC
                   -- Impossible.
-                  ModeInit  -> error "scanEvents: GCStatsGHC ModeInit"
+                  ModeInit  -> errorAs "scanEvents: GCStatsGHC ModeInit" dGC
                   ModeGHC{} -> -- error "scanEvents: GCStatsGHC ModeGHC"
                                dGC  -- workaround for #46
                   -- The last two cases are copied from case @GlobalSyncGC@
@@ -917,8 +921,9 @@ accumEvent !statsAccum (CapEvent mcap ev) =
                    in sd { dGCTable = IM.insert cap newTime dGCTable
                          , dGCMain = Just newMain
                          }
-                 ModeEnd   -> error "scanEvents: EndGC ModeEnd"
-                 ModeIdle  -> error "scanEvents: EndGC ModeIdle"
+                 ModeEnd   -> errorAs "scanEvents: EndGC ModeEnd" sd
+                 ModeIdle  -> errorAs "scanEvents: EndGC ModeIdle"
+                              $ sd { dGCTable = IM.insert cap endedGC dGCTable }
           SparkCounters crt dud ovf cnv fiz gcd _rem ->
             -- We are guranteed the first spark counters event has all zeroes,
             -- do we don't need to rig the counters for maximal interval.