Integer overflow in array allocation

[josefs]

When asked to create a sufficiently large array ghci coredumps.

\begin{code}
import Data.Array.ST
import Control.Monad.ST
import GHC.Base

example = runST (do arr <- newArray (minInt,maxInt) 
False
		    go arr)
  where go :: STArray s Int Bool -> ST s Bool
	go arr = readArray arr 3
\end{code}

Load this into ghci and type 'example'.

[simonmar]

Logged In: YES 
user_id=48280

There may be several problems here.   One is integer
overflow in Storage.c:allocate() when calculating the number
of blocks for the allocation request.  

Another problem is integer overflow in rangeSize: the
rangeSize for (minInt,maxInt) doesn't fit in an Int.  I'm
not sure what the correct outcome should be.  I'll look into
this some more later.

[simonmar]

see also #770

[simonmar]

see also #871

[StefanWehr]

With ghci 6.10.4 on Linux the problem no longer occurs. (You get an "Exception: Error in array index" instead of a core dump.) The bug seems to be fixed but I did not dare to change the status.

[simonmar]

Thanks Stefan!

[josef]

Using the bounds (minInt,maxInt) was probably the wrong thing todo. My concern when filing the bug report was not the arithmetic overflow but the fact that ghci crashes when it tries to allocate a too large an array. It is still possible to provoke a crash if you change the array bounds to, say, (2,maxInt). Should I open a new ticket or reopen this one?

[simonmar]

Ok, re-opening.