[commit: ghc] master: Fix #8754 in a round-about way. (5023c91)

[Simon Peyton Jones]

Austin, eek... you really need a Note [Need to initialise the hooks], a significant comment, and an explicit mention of this ticket.  Otherwise someone in 2 yrs time will have no clue why that lonely call to defaultsHook is so important, nor will be confident enough to remove it when the hookery is done better.

I have gotten into habit of writing a Note about virtually any fix.  After all, it is by definition not obvious or we'd have got it right the first time.  And I have too often re-invented the wheel when looking at Note-free code; or thanked the author when I read a Note and thought "ah, *that's* why!".   I wrote up some of this here https://ghc.haskell.org/trac/ghc/wiki/Commentary/CodingStyle

I don't think the commit log is enough.  git annotate may or may not lead you to the right comment, depending on how heavily modified that code is.

Thanks

Simon 

| -----Original Message-----
| From: ghc-commits [mailto:ghc-commits-bounces at haskell.org] On Behalf Of
| git at git.haskell.org
| Sent: 17 February 2014 07:49
| To: ghc-commits at haskell.org
| Subject: [commit: ghc] master: Fix #8754 in a round-about way. (5023c91)
| 
| Repository : ssh://git@git.haskell.org/ghc
| 
| On branch  : master
| Link       :
| http://ghc.haskell.org/trac/ghc/changeset/5023c91780e90947680fe0640f7564
| a4f6448bea/ghc
| 
| >---------------------------------------------------------------
| 
| commit 5023c91780e90947680fe0640f7564a4f6448bea
| Author: Austin Seipp <austin at well-typed.com>
| Date:   Sun Feb 16 19:10:16 2014 -0600
| 
|     Fix #8754 in a round-about way.
| 
|     For some reason on OS X, it seems like -Bsymbolic (which we use for
|     hooks into the RTS) isn't working, which results in #8754, where
| stats
|     don't work because defaultHooks doesn't initialize the stats flag.
| This
|     seems to work on Linux static/dynamically, but only on OS X
| statically.
| 
|     After talking with Simon, really, the entire hooks thing is a bit
|     fragile. For now, we just work around it (since GHCi is dynamically
|     linked) by calling into the defaultHooks ourselves when GHC starts.
| 
|     Signed-off-by: Austin Seipp <austin at well-typed.com>
| 
| 
| >---------------------------------------------------------------
| 
| 5023c91780e90947680fe0640f7564a4f6448bea
|  ghc/Main.hs |    4 ++++
|  1 file changed, 4 insertions(+)
| 
| diff --git a/ghc/Main.hs b/ghc/Main.hs
| index 868042b..1aa6553 100644
| --- a/ghc/Main.hs
| +++ b/ghc/Main.hs
| @@ -1,4 +1,5 @@
|  {-# OPTIONS -fno-warn-incomplete-patterns -optc-DNON_POSIX_SOURCE #-}
| +{-# LANGUAGE ForeignFunctionInterface #-}
| 
|  -----------------------------------------------------------------------
| ------
|  --
| @@ -76,6 +77,7 @@ import Data.Maybe
| 
|  main :: IO ()
|  main = do
| +   defaultsHook
|     hSetBuffering stdout LineBuffering
|     hSetBuffering stderr LineBuffering
|     GHC.defaultErrorHandler defaultFatalMessager defaultFlushOut $ do @@
| -818,3 +820,5 @@ unknownFlagsErr fs = throwGhcException $ UsageError $
| concatMap oneError fs
|          (case fuzzyMatch f (nub allFlags) of
|              [] -> ""
|              suggs -> "did you mean one of:\n" ++ unlines (map ("  " ++)
| suggs))
| +
| +foreign import ccall safe "defaultsHook" defaultsHook :: IO ()
| 
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