Re: [GHC] #15595: Stack overflow in withArgs leads to infinite memory-consuming loop

3 Sep 2018

      #15595: Stack overflow in withArgs leads to infinite memory-consuming loop
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        Reporter:  NeilMitchell   |                Owner:  (none)
            Type:  bug            |               Status:  new
        Priority:  normal         |            Milestone:  8.6.1
       Component:  Compiler       |              Version:  8.5
      Resolution:                 |             Keywords:
Operating System:  Windows        |         Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash  |            Test Case:
      Blocked By:                 |             Blocking:
 Related Tickets:                 |  Differential Rev(s):
       Wiki Page:                 |
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Comment (by osa1):

 The reason why the original code loops while my first example doesn't is
 because I don't use `getArgs`. `getArgs` calls this function:

 {{{#!haskell
 withProgArgv :: [String] -> IO a -> IO a
 withProgArgv new_args act = do
   pName <- System.Environment.getProgName
   existing_args <- System.Environment.getArgs
   bracket_ (setProgArgv new_args)
            (setProgArgv (pName:existing_args))
            act
 }}}

 The `setProgArgv new_args` part is where we get a stack overflow, but it's
 evaluated in masked state because of `bracket_`:

 {{{#!haskell
 bracket_ before after thing = bracket before (const after) (const thing)

 bracket before after thing =
   mask $ \restore -> do
     a <- before
     r <- restore (thing a) `onException` after a
     _ <- after a
     return r
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15595#comment:3
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