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List:       pcc-list
Subject:    Re: Symbol table implementation in PCC
From:       Anders Magnusson <ragge () ludd ! ltu ! se>
Date:       2010-06-03 9:09:39
Message-ID: 4C077153.2000808 () ludd ! ltu ! se
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Hi again Tony,

a hint is to subscribe to the mailing list so that I don't have to 
approve all mails you send  :-) 

Tony Cui wrote:

> > Anders Magnusson <ragge <at> ludd.ltu.se> writes:
> >   
> >
> > Hi Anders,
> >   I feel really lucky that I find you here over the internet!! Your comments is
> > very useful to me, and I have solved that problem within 6 hours. I will
> > certainly keep posting interesting questions here, as I move further with PCC
> > compiler. 
> >   Here comes one: 
> > (you mentioned in your reply..)
> >
> >   
>   
>>> >>> The local variables are stored in temporary memory that is free'd when 
>>> >>> the function is parsed. 
>>> >>>       
>>>       
>> >>   
>> >>     
>>     
> >   I did not really get this part.
> >   Do you mean that symbol table information for variables local to a function
> > (perhaps parameters included?) are deleted after the current function is parsed,
> > so these information can not be accessed later?  
>   
Exactly.  It's even more exciting; the information about local variables 
are removed as soon
as the block it was declared in is ended.  For example:

x() {
    int a;
    {
       int b;
          ....
    } <- Here is b free'd and forgotten.
} <- Here is a forgotten.


> > If that is what happened, would
> > the compiler need these symbol table information (e.g. local variables) later
> > for code generation and code optimization? 
> >   Thanks again..
> >   
>   
The variables are converted to an internal representation when they are 
found.  In the above
example both a and b would be TEMP nodes with correct type and 
individual numbers, which
is everything needed for next pass.

-- Ragge

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