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Date: Sun, 23 Aug 2009 22:47:49 +0200
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Subject: How to handle hand along data in PHP's parser?
From: php@stefan-marr.de (Stefan Marr)

Hi internals:

Currently, I try to port my Traits patch to the latest version of trunk.
Thought about giving you people the chance to play with it again.
Unfortunately, I have some trouble with the parser.
Think, there must have changed quite something in its internal working.

The last time I touched it, I had no problems handing around pointers  
in $$.u.var,
but nowadays, it looks like it is overwritten before it can be used by  
the other grammar rule.

The original idea was to construct as many data during the compilation  
phase to avoid introducing a whole of a lot new opcodes.
But, I am grateful for all suggestion about alternative implementation  
strategies.

For the problem at hand, here some code:

<code>
trait_adaptation_statement:
/* here I emit a opcode to add a new alias or precedence rule to a  
class */
   trait_precedence ';'	{ zend_add_trait_precedence(&$1 TSRMLS_CC); }
| trait_alias ';'	{ zend_add_trait_alias(&$1 TSRMLS_CC); }
;

trait_precedence:
/* This rule constructs a struct with the necessary data and should  
return
    a pointer to it in $$.u.var */
   trait_method_reference_fully_qualified T_INSTEAD  
trait_reference_list	
     { zend_prepare_trait_precedence(&$$, &$1, &$3 TSRMLS_CC); }
;

trait_reference_list:
   fully_qualified_class_name
     { zend_init_list(&$$.u.var, Z_STRVAL($1.u.constant) TSRMLS_CC); }
|  trait_reference_list ',' fully_qualified_class_name
     { zend_add_to_list(&$1.u.var, Z_STRVAL($3.u.constant) TSRMLS_CC);  
$$ = $1; }
;

trait_method_reference_fully_qualified:
   fully_qualified_class_name T_PAAMAYIM_NEKUDOTAYIM T_STRING
   { zend_prepare_reference(&$$, &$1, &$3 TSRMLS_CC); }
;
</code>

The code is basically unchanged from http://www.stefan-marr.de/traits/traits.patch


My problem starts already with trait_method_reference_fully_qualified.
I am not able to get the struct which I assigned to $$.u.var in   
trait_precedence.
 From what XCode tells me, the memory location of $$ gets overwritten  
before.
Think, it is on the stack somewhere and does not survive long enough  
to be
available in trait_precedence.


Any thoughts on that?

Many thanks and best regards
Stefan