Tue Aug 18 12:42:11 CEST 2009

Dynamic scope and thread-local variables.

Dynamic scoping is easy to implement using global variables and
save/restore combined with some `dynamic-wind' guard for longjmp() in
case that's used.

However, in the presence of pre-emptive threads, this isn't an
option.  So how to use thread-local storage?

[1] http://en.wikipedia.org/wiki/Thread-local_storage
[2] http://publib.boulder.ibm.com/infocenter/iseries/v6r1m0/index.jsp?topic=/rzahw/rzahwex1.htm