I was recently alerted of a camlp4 bug in 3.11 :
http://caml.inria.fr/mantis/view.php?id=4673
I've written a fix [1] (wich I will submit to mantis as soon as I
understand how to),
but the reporter complained that it was difficult for him to recompile the whole
ocaml distribution (Windows syndrome).

Thus, I produced a workaround syntax extension [2] that fixes the bug without
modifying the distribution : just add the extension at preprocess-time and
it should go fine. In case someone is interested, I'm posting it on the list.
Beware, this is three-hour-old code that wasn't properly tested.

Files and html pretty-print for online reading at
http://bluestorm.info/camlp4/objcopy-fix/list.php
[1] http://bluestorm.info/camlp4/objcopy-fix/Camlp4OCamlRevisedParser.ml.diff
[2] http://bluestorm.info/camlp4/objcopy-fix/pa_objcopy_bugfix.ml