strace breaks cabal - how to find the problem?

[Robin Green]

On my obscure configuration (GHC 6.10.1, with pkgenv activated, on
Fedora Linux rawhide running on a VirtualBox x86 VM with hardware
virtualisation enabled), running strace on cabal causes it to
misbehave, as described below.

I don't know whether this is due to a bug in cabal, the GHC
runtime, strace, the Linux kernel, VirtualBox, or my processor's
virtualization support. Not sure how to proceed to debug this. Perhaps
someone else could try this, on their configuration, and report what
they find?

This command is ran in an untarred copy of hs-bibutils 0.1 (not that it
matters):

strace -f -e trace=file cabal install
--extra-include-dirs=../bibutils_4.1/lib/ 2>&1|cat >cabal.strace

Cabal fails to determine the version of ghc-pkg (or sometimes ghc), and
stops, complaining that it can't verify that the version of ghc(-pkg)
is the required one. ghc-pkg is execve'd, but something goes wrong -
not sure what.
-- 
Robin