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[2001-09-04 12:50 UTC] kai dot brockmann at 3und20 dot net
[2001-09-04 12:52 UTC] kai dot brockmann at 3und20 dot net
[2002-02-04 02:25 UTC] yohgaki@php.net
[2002-03-06 00:00 UTC] php-bugs at lists dot php dot net
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Last updated: Sun Dec 22 11:01:30 2024 UTC |
I'm working with an Access 2000 database (MDAC 2.6) via ODBC on W2K SP2. The following code will cause PHP 4.0.6 to crash with an access violation. The same bahaviour was experienced with version 4.0.2. Save the two files and open test.php in browser to reproduce. (Sorry, must post long script as I haven't any other place to put it. And I got no gdb.) -------------------------------------- crash code: test.php <html> <body> <?php include('test2.php'); causeAccessViolation(); ?> </body> </html> -------------------------------------- crash code: test.php END -------------------------------------- crash code: test2.php <?php function connect() { // Put some db here; my DNS was 'eqms' $db = odbc_connect('eqms', '', '') or die(__FILE__.": Unable to connect to database!"); return $db; } function disconnect($db) { if(isset($db) && $db != 0) odbc_close($db); } function denyAccess() { echo 'NO ACCESS'; exit(); } function causeAccessViolation() { $db = connect(); if(!$db) die($db_err); // Put some query here $query = "SELECT MitarbeiterID, ProjektID FROM ProjektMitarbeiter WHERE MitarbeiterID = 45 AND ProjektID = 45"; $query_result = odbc_exec($db, $query); if(!$query_result) die($db_err); $row = odbc_fetch_row($query_result); /* 1 odbc_free_result($query_result); disconnect($db); */ denyAccess(); /* 2 COMMENT OUT THE NEXT TWO LINES AND COMMENT IN THE LINES AT 1 AND PHP WON'T CRASH ANYMORE */ odbc_free_result($query_result); disconnect($db); } ?> -------------------------------------- crash code: test2.php END I debugged PHP and the results showed that PHP crashed during shutdown somewhere below list_entry_destructor() in zend_list.c: ----------------- snippet zend_list.c void list_entry_destructor(void *ptr) { zend_rsrc_list_entry *le = (zend_rsrc_list_entry *) ptr; zend_rsrc_list_dtors_entry *ld; if (zend_hash_index_find(&list_destructors, le->type,(void **) &ld)==SUCCESS) { switch (ld->type) { case ZEND_RESOURCE_LIST_TYPE_STD: if (ld->list_dtor) { (ld->list_dtor)(le->ptr); } break; case ZEND_RESOURCE_LIST_TYPE_EX: if (ld->list_dtor_ex) { ld->list_dtor_ex(le); /******** CRASH HERE ********/ } break; EMPTY_SWITCH_DEFAULT_CASE() } } else { zend_error(E_WARNING,"Unknown list entry type in request shutdown (%d)",le->type); } } ----------------- snippet zend_list.c END When I dug a bit deeper I saw the following happening: ld->list_dtor_ex had the follwing values on two consecutive calls: First: _close_odbc_conn(_zend_rsrc_list_entry *) Second: _free_odbc_result(_zend_rsrc_list_entry *) ----> after that some ODBC32 functions are called then CRASH BUT on another page that didn't cause PHP to crash and utilized odbc, it had the following values on three consecutive calls: First: _free_odbc_result(_zend_rsrc_list_entry *) Second: _file_fopen_dtor(_zend_rsrc_list_entry *) Third: _close_odbc_conn(_zend_rsrc_list_entry *) I'm no expert for the PHP source (was the first time I saw it, actually) but I imagine the crash has something to do with the wrong order of the calls, if it's not something with the odbc drivers (Jet...). Especially, notice that, when you change the position of the two lines that free the odbc result and close the connection, PHP behaves normally (see test2.php). hope that helps, kai