Parse tree creation question

Hi,


I am creating my abstract syntax tree with bison. I have some rules like
this:


a: b c { $$ = gProgram = new a( $1, $2 ); } ;
b: d { $$ = new b( $1 ); } ;
c: e { $$ = new c( $1 ); } ;


Now, if the parsing phase doesn't fail, when a gets reduced, gProgram
is a pointer to the entire parse tree, so I can't deallocate it when I
am done working with it. But, if the parsing phase fails for any
reason, I can't deallocate the nodes constructed up to the momento of
failure, since I have no pointer to them.


Any help on how to remedy this would be extremely helpful.


Thank you very much,
Nicols


PS: I thought the possibility of creating an object "pool", and
allocating the objects from there. That way I could maintain a list of
created objects and deallocate them when I am done. But I don't know if
this is the best approach.
[That's what I do, in compilers where I do enough work after a parse
failure to go to the effort of freeing the space. -John]

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