Subj : The root of the syntax tree
To   : netscape.public.mozilla.jseng
From : joao
Date : Tue Jul 06 2004 11:56 pm

Hi all,

I'm trying to get at the syntax tree, after a JS script has been
compiled. Hopefully I'd like to have a tool to display and manipulate
this tree.

I've been poking around the SpiderMonkey source code (I downloaded the
latest js-1.5-rc6a), I found the description of JSParseNode's in
jsparse.h, so I've written a little recursive function that outputs a
node, showing token type, jsop, arity, and the children if any.

Then to have this code called, I looked into js_CompileTokenStream in
jsparse.c, and added my call after the line that says

     pn = Statements(cx, ts, &cg->treeContext);

It turns out that this node only has a TOK_EOF... I was hoping to find
a list of top-level statements. So I went one step further, inside the
Statements call, and inserted my call inside the 'while' loop, after
the line

         pn2 = Statement(cx, ts, tc);

and sure enough, I can output each of the toplevel statements. But they
are not connected, I do not have a root for this syntax tree. Does this
root exist ? are all the top-level statements collected somewhere,
before the EOF is reached ? or does JS emit the bytecode for each
statement and then forget about it ?

Related question : for a string literal, I get a TOK_STRING token with
a JSOP_STRING operator, but I can't see how to get at the value of the
string ; it has arity PN_NULLARY so there's nothing more in the
JSParseNode. How can I reach this value ?

Thanks,
Joao

-- 
joao at teaser dot fr

.