Description:
------------
When using @list( $b ) = $a; on PHP 6, it seems that a new opcode is inserted that frees a temp variable set from $a (see the "Actual result" section below) and thus segfaults when using $a later. When I set breakpoints on all lines that contains "SWITCH_FREE" in Zend_execute.c, it's the one at line 1170 in function zend_do_free() that is called.

Reproduce code:
---------------
<?php
$a = array( "c" );
@list( $b ) = $a;
var_dump( $a );

I also used vld to get the opcodes produced by the laguage parser.

Expected result:
----------------
array(1) {
  [0]=>
  string(1) "c"
}

Analyse with vld:
$ PHP_5_3/sapi/cli/php -dvld.active=1 ~/test.php
Branch analysis from position: 0
Return found
filename:       /Users/alexandre/test.php
function name:  (null)
number of ops:  11
compiled vars:  !0 = $a
line     #  op                           fetch          ext  return  operands
-------------------------------------------------------------------------------
   2     0  INIT_ARRAY                                       ~0      'c'
         1  ASSIGN                                                   !0, ~0
   3     2  BEGIN_SILENCE                                    ~2      
         3  FETCH_R                      local               $4      'a'
         4  FETCH_DIM_R                                      $5      $4, 0
         5  FETCH_W                      local               $3      'b'
         6  ASSIGN                                                   $3, $5
         7  END_SILENCE                                              ~2
   4     8  SEND_VAR                                                 !0
         9  DO_FCALL                                      1          'var_dump'
   5    10  RETURN                                                   1

Actual result:
--------------
Segmentation fault.

Analyse with vld:
$ PHP_6/sapi/cli/php -dvld.active=1 ~/test.php
Branch analysis from position: 0
Return found
filename:       /Users/alexandre/test.php
function name:  (null)
number of ops:  12
compiled vars:  !0 = $a
line     #  op                           fetch          ext  return  operands
-------------------------------------------------------------------------------
   2     0  INIT_ARRAY                                       ~0      c
         1  ASSIGN                                                   !0, ~0
   3     2  BEGIN_SILENCE                                    ~2      
         3  FETCH_R                      local               $4      a
         4  FETCH_DIM_TMP_VAR                                $5      $4, 0
         5  FETCH_W                      local               $3      b
         6  ASSIGN                                                   $3, $5
         7  END_SILENCE                                              ~2
         8  SWITCH_FREE                                              $4
   4     9  SEND_VAR                                                 !0
        10  DO_FCALL                                      1          var_dump
   5    11  RETURN                                                   1

You can see the new opcode "SWITCH_FREE" at position 8.