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Date: Mon, 07 Mar 2005 18:38:56 -0800
To: "Sara Golemon" <pollita@php.net>,internals@lists.php.net
In-Reply-To: <20050307221330.17528.qmail@lists.php.net>
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Subject: Re: [PHP-DEV] Using `throw` with expr or expr logic
From: andi@zend.com (Andi Gutmans)
References: <20050307221330.17528.qmail@lists.php.net>

Hey Sara,

Nothing to ridicule but there's a good reason that currently throw is a 
statement. It has to do with us not being able to clean up properly when 
we're within an expression as far as memory leaks, reference counting and 
other locks are concerned.
Theoretically your patch could be applied as it's not the worst thing 
(there are other existing situations where such edge cases could be 
triggered) but I think it's better to keep the current state. I'd also have 
to check if there aren't actually real additional problems (misbehaviors) 
that could occur.
I must say that I am debating with myself on this issue as syntactically 
it's nice but I'm worried of the implications. It requires some thorough 
analysis.

Andi

At 02:13 PM 3/7/2005 -0800, Sara Golemon wrote:
>A user was asking about why he could perform statements such as:
>
>$db = mysql_connect('localhost') or die('Unable to connect to database
>server');
>
>But not:
>
>$db = new mysqli('localhost') or throw('Unable to connect to database
>server');
>
>The short answer, obviously, is that throw just doesn't behave that way.
>Like echo(), it simply doesn't have a return value to give.
>
>Then again.... neither do die() or exit(), yet they pretend to return
>one....
>
>I've tried out the patch below with `make test` and it doesn't complain of
>anything.  Can a ZendHead take a look and ridicule or otherwise comment?
>
>-Sara
>
>
>Index: Zend/zend_compile.h
>===================================================================
>RCS file: /repository/ZendEngine2/zend_compile.h,v
>retrieving revision 1.302
>diff -u -r1.302 zend_compile.h
>--- Zend/zend_compile.h 11 Feb 2005 22:26:45 -0000 1.302
>+++ Zend/zend_compile.h 7 Mar 2005 22:08:49 -0000
>@@ -396,7 +396,7 @@
>  void zend_do_try(znode *try_token TSRMLS_DC);
>  void zend_do_begin_catch(znode *try_token, znode *catch_class, znode
>*catch_var, zend_bool first_catch TSRMLS_DC);
>  void zend_do_end_catch(znode *try_token TSRMLS_DC);
>-void zend_do_throw(znode *expr TSRMLS_DC);
>+void zend_do_throw(znode *result, znode *expr TSRMLS_DC);
>
>  ZEND_API int do_bind_function(zend_op *opline, HashTable *function_table,
>zend_bool compile_time);
>  ZEND_API zend_class_entry *do_bind_class(zend_op *opline, HashTable
>*class_table, zend_bool compile_time TSRMLS_DC);
>Index: Zend/zend_compile.c
>===================================================================
>RCS file: /repository/ZendEngine2/zend_compile.c,v
>retrieving revision 1.614
>diff -u -r1.614 zend_compile.c
>--- Zend/zend_compile.c 6 Mar 2005 16:22:02 -0000 1.614
>+++ Zend/zend_compile.c 7 Mar 2005 22:08:49 -0000
>@@ -1670,7 +1670,7 @@
>   CG(active_op_array)->opcodes[try_token->u.opline_num].extended_value =
>get_next_op_number(CG(active_op_array));
>  }
>
>-void zend_do_throw(znode *expr TSRMLS_DC)
>+void zend_do_throw(znode *result, znode *expr TSRMLS_DC)
>  {
>   zend_op *opline;
>
>@@ -1678,6 +1678,10 @@
>   opline->opcode = ZEND_THROW;
>   opline->op1 = *expr;
>   SET_UNUSED(opline->op2);
>+
>+ result->op_type = IS_CONST;
>+ result->u.constant.type = IS_BOOL;
>+ result->u.constant.value.lval = 1;
>  }
>
>  ZEND_API void function_add_ref(zend_function *function)
>Index: Zend/zend_language_parser.y
>===================================================================
>RCS file: /repository/ZendEngine2/zend_language_parser.y,v
>retrieving revision 1.155
>diff -u -r1.155 zend_language_parser.y
>--- Zend/zend_language_parser.y 11 Feb 2005 22:26:45 -0000 1.155
>+++ Zend/zend_language_parser.y 7 Mar 2005 22:08:49 -0000
>@@ -110,7 +110,7 @@
>  %token T_RETURN
>  %token T_TRY
>  %token T_CATCH
>-%token T_THROW
>+%right T_THROW
>  %token T_USE
>  %token T_GLOBAL
>  %right T_STATIC T_ABSTRACT T_FINAL T_PRIVATE T_PROTECTED T_PUBLIC
>@@ -225,7 +225,6 @@
>    T_VARIABLE ')' { zend_do_begin_catch(&$1, &$9, &$11, 1 TSRMLS_CC); }
>    '{' inner_statement_list '}' { zend_do_end_catch(&$1 TSRMLS_CC); }
>    additional_catches { zend_do_mark_last_catch(&$7, &$18 TSRMLS_CC); }
>- | T_THROW expr ';' { zend_do_throw(&$2 TSRMLS_CC); }
>  ;
>
>
>@@ -614,6 +613,7 @@
>   | T_ARRAY '(' array_pair_list ')' { $$ = $3; }
>   | '`' encaps_list '`'  { zend_do_shell_exec(&$$, &$2 TSRMLS_CC); }
>   | T_PRINT expr  { zend_do_print(&$$, &$2 TSRMLS_CC); }
>+ | T_THROW expr  { zend_do_throw(&$$, &$2 TSRMLS_CC); }
>  ;
>
>  function_call
>
>--
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