> Are you using any C bindings which create custom blocks?  That error  
 > occurs if your custom block does not define a serialization function  
 > (documented here: http://caml.inria.fr/pub/docs/manual-ocaml/ 
 > manual032.html#s:custom).

Thanks; at least now I have some idea what's happening.

I'm not aware of using any C bindings at all, although I am linking
against the Unix library.  My final executable does contain
definitions of caml_alloc_custom, caml_register_custom_operations, and
related functions, but none of my .o or .a files refers to such a
function.

Any ideas how I might track down the source of a custom block?


Norman