Hey,
On Wed, 26 Nov 2003, Andi Gutmans wrote:
> Now that we're at a very advanced stage and the code freeze is coming up, I
> think it'd be a good idea to start running some PHP 4 applications on PHP 5
> and see how easy things go. I'm sure we'll bump into some issues and many
> of them might be solvable (using the already existing compatibility mode
> for object cloning or by other means).
There is one major problem that I see at this moment, and that is the
problem with shutdown order and destructors.
Problem 1:
extension=mysql.so
<?php
class foo {
private $c;
function __construct() {
$this->c = mysql_connect();
}
function __destruct() {
mysql_close($this->c);
}
}
$f = new foo();
?>
This little script will give you a nice unresolved symbol when doing the
mysql_close as the extensions are unloaded before the dtors run.
Problem 2:
The following script:
<?php
class A {
public function __destruct() {
echo "destructor!\n";
}
}
$obj = new A();
echo "I'm alive!\n";
?>
crashes Xdebug. While I thought it was *my* bug, it turned out to have
the same cause as problem 1: the dtor is run after the GET/POST/COOKIE
var tables are destroyed. (Xdebug tries to check some things in there on
every function call). It's not only this, see problem 3.
788 zend_hash_find(PG(http_globals)[TRACK_VARS_GET]->value.ht,
"XDEBUG_SESSION_START", sizeof("XDEBUG_SESSION_START"), (void **) &dummy) == SUCCESS
(gdb) bt
#0 0x0826325d in _zend_is_inconsistent (ht=0x5a5a5a5a,
file=0x8417660 "/dat/dev/php/php-5.0dev/Zend/zend_hash.c", line=841)
at /dat/dev/php/php-5.0dev/Zend/zend_hash.c:53
#1 0x082656f1 in zend_hash_find (ht=0x5a5a5a5a,
arKey=0x406446bd "XDEBUG_SESSION_START", nKeyLength=21, pData=0xbfffe70c)
at /dat/dev/php/php-5.0dev/Zend/zend_hash.c:841
#2 0x406325dd in xdebug_execute (op_array=0x405f9000)
at /dat/dev/php/xdebug/xdebug.c:788
#3 0x08252cd3 in zend_call_function (fci=0xbfffec20, fci_cache=0x0)
at /dat/dev/php/php-5.0dev/Zend/zend_execute_API.c:737
(gdb) frame 3
#3 0x08252cd3 in zend_call_function (fci=0xbfffec20, fci_cache=0x0)
at /dat/dev/php/php-5.0dev/Zend/zend_execute_API.c:737
737 zend_execute(EG(active_op_array) TSRMLS_CC);
(gdb) print *executor_globals.active_op_array
$2 = {type = 2 '\002', function_name = 0x405f5608 "__destruct",
scope = 0x405f7518, fn_flags = 16640, prototype = 0x0, num_args = 0,
arg_info = 0x0, pass_rest_by_reference = 0 '\0', refcount = 0x405f792c,
opcodes = 0x405f7968, last = 5, size = 5, T = 0, brk_cont_array = 0x0,
last_brk_cont = 0, current_brk_cont = 4294967295, static_variables = 0x0,
start_op = 0x0, backpatch_count = 0, return_reference = 0 '\0',
done_pass_two = 1 '\001', uses_this = 0 '\0',
filename = 0x405f5d8c "/dat/dev/php/xdebug/tests/bug00001.php",
line_start = 3, line_end = 5, doc_comment = 0x0, doc_comment_len = 0,
reserved = {0x0, 0x1, 0x8414a60, 0x923}}
Problem 3:
All extension globals are also destroyed before destructors run:
0x40631ac0 in add_stack_frame (zdata=0xbfffeb80, op_array=0x405f9000, type=0)
at /dat/dev/php/xdebug/xdebug.c:684
684 xdebug_llist_insert_next(XG(stack), XDEBUG_LLIST_TAIL(XG(stack)), tmp);
(gdb) bt
#0 0x40631ac0 in add_stack_frame (zdata=0xbfffeb80,
op_array=0x405f9000,
type=0) at /dat/dev/php/xdebug/xdebug.c:684
#1 0x40632040 in xdebug_execute (op_array=0x405f9000)
at /dat/dev/php/xdebug/xdebug.c:830
#2 0x08252cd3 in zend_call_function (fci=0xbfffec20, fci_cache=0x0)
at /dat/dev/php/php-5.0dev/Zend/zend_execute_API.c:737
(gdb) print xdebug_globals.stack
$2 = (xdebug_llist *) 0x0
(this variable is initialized in MINIT and destroyed in MSHUTDOWN).
Parts of a chat with Zeev about this:
12:11 <@Derick> the hook you added "exec_finished" didn't solve my problem
12:11 <@Derick> because destructors are still called AFTER RSHUTDOWN :(
12:11 <@Zeev> they're not supposed to
12:11 <@Zeev> but I didnt do anything beyond exec_finished
12:11 <@Zeev> that is, nothing uses it yet
12:11 <@Derick> so what's the point of it ? :)
12:11 <@Zeev> the point is that it solves the problem
12:11 <@Zeev> once things start using it :)
12:12 <@Zeev> I can barely type
12:12 <@Zeev> my fingers are on fire
12:12 <@Derick> well, then the ZE needs to be modified to use it ;)
12:12 <@Derick> Zeev: peppers?
12:12 <@Zeev> derick the engine isnt supposed to use it
12:12 <@Derick> heh
12:12 <@Zeev> it simply has to call destructors after exec_finished
12:12 <@Zeev> but before rshutdown
12:12 <@Derick> yes
12:13 <@Zeev> but we cant do that before modules like the session module implement
exec_finished
12:13 <@Derick> doesn't that need an engine mod then?
12:13 <@Derick> Zeev: ah ha
12:13 <@Zeev> because they're the reason destructors are called after rshutdown to
begin with
12:13 <@Zeev> and yeah
12:13 <@Derick> Zeev: the problem is that if you mod session, the stuff needs to work
first ... it's a chicken and egg problemm
Related test case:
14:46 <@Derick> ZE2 accessing globals from destructor in shutdown
[tests/classes/destructor_and_globals.phpt]
14:46 <@Derick> Andi_: thats the one I told you about a couple of days ago btw
regards,
Derick
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