heap overflow should generate an exception

[guest]

I want to use the -M option for the goals that are stated in the manual.

./TestProgram +RTS -M5m -RTS 

Expected output:

Something like "out of heap space"

Actual result:

Machine going into a state where it swaps memory 

This is the code for TestProgram?:

import Control.Monad.ST 
import Data.Array.ST
import Data.Array.MArray
import Data.Array.Base(unsafeNewArray_)
main = print (runST (do make_empty_table >> return ()))

make_empty_table::  ST s (STArray s (Int, Int) (Maybe ep))
make_empty_table = 
       unsafeNewArray_ ((1, 1), (16384, 16384))

This was tested with 6.9.20071018 on an athlon-xp, and confirmed by dcoutts also on x86-64 with ghc-6.8.0.20071015.

[simonmar]

Fixed, thanks!

Wed Oct 24 10:54:20 BST 2007  Simon Marlow <simonmar@microsoft.com>
  * FIX #1791: fail with out-of-heap when allocating more than the max heap size in one go

[igloo]

Merged

[guest]

I actually expected to get an exception stating "out of heap", like it also works for stack overflows. I have a catch all exception catcher, but this one isn't triggered. Also the actual output doesn't state it's an exception, so I guess it really is not. So, I am reopening it again. Again, to be clear: I want that

Control.Exception.catch 
         action 
         (\exception -> do 
           appendFile "/home/me/exception" (show exception)
           return Nothing)

where action contains the code that overflows the heap does not result in a complete program failure, it should just be a _local_ problem (i.e. an exception). This also means that the test case is likely to be wrong.

[simonmar]

Correct - heap overflow doesn't currently generate an exception. It's something we should really do, but it isn't completely clear how to do it. For example, in order to run the exception handler, you need some heap space. So perhaps you want a "soft" and a "hard" limit on heap space, and to get an exception when the "soft" limit is reached.

Another question is: which thread(s) should get the exception?

[demetrix]

Replying to simonmar:

Another question is: which thread(s) should get the exception?

Why not the thread currently executing IO action which failed to allocate memory? Such behaviour would be the same as in almost any other programming language. Perhaps the only potential problem here is when additional threads are spawned not explicitely with forkIO or forkOS but rather implicitely with par - maybe in that case the thread which forces the evaluation of the "parallel" value should get the exception?