GENSYM is Harder than You Think

How does one implements GENSYM^[1] in a robust and thread safe way? What if several programs have to interchanged generated SEXPs, so that symbols wont clash? Say two different compilers gensyming assembly output may produce clashing identifiers.

[1] http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Body/fun_gensym.html

>>6
By locking the symbol table when interning a new symbol.
What if we use bare-string instead and program runs across a network of several machines, each having own symbol table?

Windows uses http://en.wikipedia.org/wiki/Globally_unique_identifier but I fail to get how they are robust and synced.

Force symbols gensymed by different programs to reside in different packages.
printed SEXPs dont have packages.