mallocPlainForeignPtrBytes -1000 gives runtime internal error: allocGroup: requested zero blocks

Passing negative numbers to mallocPlainForeignPtrBytes causes the following to appear:

Test: internal error: allocGroup: requested zero blocks
   (GHC version 6.10.4 for i386_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
Aborted

Originally, a bug in my app meant that I called Data.ByteString.hGet with a negative 'numBytes' argument, however I've managed to boil it down to a one line test case involving just mallocPlainForeignPtrBytes as follows:

$ cat Test.hs
import GHC.ForeignPtr (mallocPlainForeignPtrBytes)
main = mallocPlainForeignPtrBytes (-1000)

$ ghc --make Test.hs 
[1 of 1] Compiling Main             ( Test.hs, Test.o )
Linking Test ...

$ ./Test
Test: internal error: allocGroup: requested zero blocks
    (GHC version 6.10.4 for i386_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
Aborted

The magnitude of the number appears to have some effect; with ghc 6.10.1 it seemed to reliably crash with numBytes <= -9. But when I upgraded to ghc 6.10.4, the test case started working. However, changing to -1000 reliably causes a crash on my box - perhaps the behaviour depends on heap layout. Either way, the function should probably behave more gracefully .. perhaps raising an exception.

Full gory details of my setup (ie. ghc -v output, gcc version) are attached because they messed up the formatting.

Trac metadata

Trac field	Value
Version	6.10.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
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