space_leak_001(ghci) segfaults on OS X x86_64

[igloo]

In 7.4 branch and HEAD, space_leak_001(ghci) segfaults on OS X x86_64.

I can reproduce it most of the time like this (with GhcDebugged=YES, GhcThreaded=NO):

$ time /Users/ian/ghc/7.4-branch/val64/inplace/bin/ghc-stage2 --interactive space_leak_001.hs +RTS -DS -C0 -V0
created capset 0 of type 2
created capset 1 of type 3
assigned cap 0 to capset 0
assigned cap 0 to capset 1
GHCi, version 7.4.0.20120126: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Main             ( space_leak_001.hs, interpreted )
Ok, modules loaded: Main.
*Main> main
Segmentation fault: 11

real    6m11.094s
user    6m7.249s
sys     0m0.195s

but if I run it under gdb then it doesn't segfault.

[igloo]

Can't reproduce it on OX X i386.