#5889: -fno-prof-count-entries leads to linking errors -------------------------------------+------------------------------------- Reporter: akio | Owner: bgamari Type: bug | Status: new Priority: highest | Milestone: 8.4.1 Component: Compiler | Version: 8.3 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 Type of failure: GHC rejects | (amd64) valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): Alright, the rest is pretty clear I think: Note that in the RHS of the simplified `newTyConInstRhs` the ticks should wrap the two arguments `ww1_suMl` and `ww2_suMm` but don't. `CoreUtils.mkTick` has the following case for ticks wrapping `Var`s, {{{#!hs mkTick' top rest expr = case expr of ... Var x | notFunction && tickishPlace t == PlaceCostCentre -> orig_expr | notFunction && canSplit -> top $ Tick (mkNoScope t) $ rest expr where -- SCCs can be eliminated on variables provided the variable -- is not a function. In these cases the SCC makes no difference: -- the cost of evaluating the variable will be attributed to its -- definition site. When the variable refers to a function, however, -- an SCC annotation on the variable affects the cost-centre stack -- when the function is called, so we must retain those. notFunction = not (isFunTy (idType x)) }}} Moreover, `CoreSyn.tickishPlace` is defined thusly, {{{#!hs tickishPlace :: Tickish id -> TickishPlacement tickishPlace n@ProfNote{} | profNoteCount n = PlaceRuntime | otherwise = PlaceCostCentre ... }}} This is how the counting and non-counting cases are treated differently. So in short, in the non-counting case we try to wrap a `Var` expression in a tick. `mkTick` then notices that such a tick can be dropped and does so. However, the tick remains in the unfolding. Consequently, when we inline `newTyConInstRhs` in another module we end up with a reference to a cost center whose corresponding symbol doesn't exist in the module that is supposed to define it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/5889#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler