Bison back-tracking

[Hans Aberg]

Is Bison deterministic or does sometimes Bison back-track? If Bison
sometimes back-track, is there a way to know when Bison is back-tracking or
to enforce determinism?

By back-tracking, I mean that there are rules
   <variable>: <rule 1> { ... } | <rule 2> { ... } ...
where Bison first investigates <rule 1> and in that course executes some of
the associated actions, then decides that rule 1 is not applicable, and
then decides for <rule 2> instead.

-- This way of acting is OK when using the $$ variables, because each
semantic (non-terminal) variable has it's own Bison $$-value.

However, when building a large global structure, such a table which should
not be copied as the $$ values are, then back-tracking will screw up that
global value. So I want way to avoid it, either by identifying when it can
occur, or preventing it all-together.

  Hans Aberg