Re: Re: [Zend Engine 2] Re: [PHP-DEV] [RESENT] [PATCH] Allow constants / expressions to be passed by reference]

Okay I'll try and look at your patch in the next couple of days. It's quite sensitive code which this changes (has harmless as it might seem) so I need some time to read over it. Andi At 11:37 29/05/2002 -0500, Jason T. Greene wrote:

Andi, I do not see how this is semantically incorrect, or how it is that much different than allowing default values for pass by reference arguments. IMO The only useful reason to deny passing a constant/expression in a function is to provide a warning message. Some of the problems I outlined in my post can be solved using default values(only using ZE2, which allows defaults on reference args); however, default values only solve rightmost optional parameters. i.e. there is no way to do: function a($arg1, $arg2="blah", $arg3="blah"){} a(1, ,3) In respect to not passing by reference, this problem is solved by doing the following function magic_function($var1, $var2, $var3) {

        // Note just an example - I would usually use func_get_args...
        if ($var2 === NULL) {
                $var2 = "blah";
        }

} magic_function(1, NULL, 3); This technique of course will not work with the current semantics of not allowing constants/expressions to pass by reference. -Jason On Wed, 2002-05-29 at 10:26, Andi Gutmans wrote: I don't see any reason to allow passing non-variables by reference. It is semantically incorrect. Andi At 09:40 29/05/2002 +0200, Stig S. Bakken wrote:

If this patch doesn't break anything, and it doesn't give us any difficulties with ZE2 or major design issues, I'm +1. - Stig On Tue, 2002-05-28 at 21:12, Jason T. Greene wrote:

Due to this patch being sent during the msession discussion, it has not been noticed, so I am resending. -Jason ----

From: Jason Greene <jason@php.net> To: php-dev@lists.php.net Cc: zeev@zend.com, andi@zend.com Subject: [PHP-DEV] [PATCH] Allow constants / expressions to be passed

by reference

Date: 25 May 2002 02:18:52 -0500 Problem ------- There are some scenarios where a function requires the ability to

modify

parameters that may also be optional. Optional parameters work well, except in the scenario where all of the pass by reference

parameters can

be optional. ex the socket_select() function. Since select is argument-result, all three arrays that are taken as input must be

passed

by reference, yet any can be excluded. So for example if you were calling socket_select with a read socket array, a write socket array, yet no exception array (quite common), you are currently forced to do something like the following: $wfds = array($sock1, $sock2); $rfds = array($sock3, $sock4); $null = NULL; socket_select($rfds, $wfds, $null); I have ran into this problem before several times while developing in user space. (Especially when passing around semi-complex data structures) Proposed Solution ------------------ Allow all expressions to be passed by reference. This will allow something like the following function normalize(&$element_tree, &$node_mapping, $max_depth){ //Code } normalize($my_tree, NULL, 25000); Patch ------ I have attached a patch against ZE2 that accomplishes this. Thanks, -Jason ----

Index: zend_compile.c =================================================================== RCS file: /repository/ZendEngine2/zend_compile.c,v retrieving revision 1.285 diff -u -r1.285 zend_compile.c

--- zend_compile.c    23 Apr 2002 18:06:53 -0000      1.285
+++ zend_compile.c    25 May 2002 06:45:21 -0000

@@ -1271,7 +1271,7 @@

                              op = ZEND_SEND_REF;
                              break;
                      default:
-                             zend_error(E_COMPILE_ERROR, "Only

variables can be passed by reference");

+                             op = ZEND_SEND_VAR;
                              break;
              }
      }

Index: zend_execute.c =================================================================== RCS file: /repository/ZendEngine2/zend_execute.c,v retrieving revision 1.341 diff -u -r1.341 zend_execute.c

--- zend_execute.c    8 May 2002 18:43:19 -0000       1.341
+++ zend_execute.c    25 May 2002 06:45:25 -0000

@@ -2292,10 +2292,6 @@

                                      NEXT_OPCODE();
                              }
                      case ZEND_SEND_VAL:
-                             if

(EX(opline)->extended_value==ZEND_DO_FCALL_BY_NAME

-                                     &&

ARG_SHOULD_BE_SENT_BY_REF(EX(opline)->op2.u.opline_num, EX(fbc), EX(fbc)->common.arg_types)) {

-                                             zend_error(E_ERROR,

"Cannot pass parameter %d by reference", EX(opline)->op2.u.opline_num);

-                             }
                              {
                                      zval *valptr;
                                      zval *value;

@@ -2329,7 +2325,8 @@

zend_ptr_stack_push(&EG(argument_stack), varptr);

                                              NEXT_OPCODE();
                                      }
-                                     zend_error(E_ERROR, "Only

variables can be passed by reference");

+                                     /* Should only occur with an

uninitialized variable */

+                                     goto send_by_var;
                              }
                              NEXT_OPCODE();
                      case ZEND_SEND_VAR:

----

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