Q: How to preserve symbol table info through multiple pass compilation?

Hi,


I'm currently writing a multiple pass (tree-based) compiler. So far
I've accomplished the following:


1) lexed input into tokens
2) parsed tokens and created a parse tree


Next I will accomplish the semantic checking and code gen with
multiple passes on the parse tree.


My question is this: what is the best way to structure a symbol table
so that the scope relationships are preserved/updated through multiple
passes of the parse tree?


I originally preserved the symbol table by saving the contents for a
specific scope at the appropriate places in the parse tree, but this
is giving me problems when I want to insert something new into the
symbol table after the initial pass through the parse tree. I am
playing around with the idea of representing the symbol table as a
tree of scopes, with nested scopes being children of the scope they
are nested in. This, however, gives me a problem with constructs like
the following:




void foo () {
...
}


int x;


void boo() {
...
}


'x' should be visible to boo but not foo even though they have the
same parent scope.


Does anyone have any suggestions? Please mail reply. Thanks!
--
Justin Lee
jlee@espresso.ucsd.edu
Interactive Cognition Lab at UCSD
(619) 822-0673
--

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