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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Changes (by osa1):

 * version:  8.4.3 => 8.5

Comment:

 I did a little bit of debugging -- basically the RTS is throwing a stack
 overflow exception, but the mutator is then trying to allocate more stack
 space (maybe because stack overflow exception is somehow masked?), causing
 a loop.

 A different variant of this program exits with a stack overflow exception:

 {{{#!haskell
 {-# LANGUAGE ForeignFunctionInterface #-}

 import Foreign.C.Types
 import Foreign.C.String
 import Foreign.C
 import Foreign.Ptr
 import GHC.Foreign (withCStringsLen)

 foreign import ccall unsafe "setProgArgv"
   c_setProgArgv  :: CInt -> Ptr CString -> IO ()

 main :: IO ()
 main = do
     putStrLn "Starting"
     withCStringsLen utf8 (replicate 1000 "") $ \len css -> do
       c_setProgArgv (fromIntegral len) css
 }}}

 Output:

 {{{
 $ ./Main +RTS -K1K
 Starting
 Main: Stack space overflow: current size 33624 bytes.
 Main: Use `+RTS -Ksize -RTS' to increase it.
 }}}

 I don't know why the `withArgs` version doesn't fail with the same error
 yet, but I think `Note [Throw to self when masked]` is relevant.

 (Confirmed on GHC HEAD so updating the version)

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15595#comment:1
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