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Bug #39344 Unnecessary calls to OnModify callback routine for an extension INI directive
Submitted: 2006-11-02 11:10 UTC Modified: 2006-11-08 11:05 UTC
From: wharmby at uk dot ibm dot com Assigned: dmitry
Status: Closed Package: Scripting Engine problem
PHP Version: 5CVS-2006-11-02 (snap) OS: Windows XP
Private report: No CVE-ID:
 [2006-11-02 11:10 UTC] wharmby at uk dot ibm dot com
Unnecessary calls to OnModify callback routine for an
extension INI directives in ZTS enabled builds.

Please note the problem reported here only applies to ZTS 
enabled builds.

I have tried the supplied testcase on the latest snap-shot 
build for Windows (Nov 2, 2006 09:30 GMT)and the problem 
persists. phpinfo() shows "PHP Version => 5.2.1-dev".

Problem also persists in latest checked in version of file 
in CVS.

If I define a OnMOdify callback routine for an extension INI
directive the routine is called multiple times during
startup even though the directive is not being continually
modified. I expected one call as a result of modification to
the directive in php.ini but instead I got 3 calls.

I spotted this behaviour reviewing the engine code whilst 
reading Sara Golemon's book "Extending and Embedding PHP" 
and include a slightly modified version of sample code
from her book to illustrate the unnecessary calls.

The first problem is that in a ZTS enabled build 
zend_ini_refresh_caches() is called twice for each new 
thread. The method zend_new_thread_end_handler() calls it 
directly as follows: 

static void zend_new_thread_end_handler(THREAD_T thread_id TSRMLS_DC)
    zend_ini_refresh_caches(ZEND_INI_STAGE_STARTUP TSRMLS_CC);

However, zend_copy_ini_directives() itself also calls zend_ini_refresh_caches() so we end up calling any OnModifty callback routines twice for each new thread.

I believe that: 
   (1) the call in zend_copy_ini_directives() can safely be
       removed, and 
   (2) the call in zend_new_thread_end_handler() should
       really be conditional on the success of the copy 
       operation, otherwise we could attempt to iterate
       over a non-existent hash and die. 

This will reduce the number of calls to 2 on ZTS emabled builds but any OnModifycallback routine will still be called twice on the startup thread in ZTS enabled builds; once by zend_register_ini_entries() during MINIT processing when an extension registers its INI directives and again on ZTS
builds during zend_post_startup() processing, i.e 

 zend_post_startup() -> zend_new_thread_end_handler()  -> 

Whilst the call to the OnModify callback routine from zend_register_ini_entries() is required for non-ZTS builds 
to work correctly I can see no need for a call from 
zend_ini_refresh_caches() during zend_post-startup 
processing. I believe this can easily be resolved by 
modifying zend_post_startup() to call 
instead of 

My patch for zend.c is here:
and for zend_ini.c here: 

Reproduce code:
Reproduce code is here:

I tested by adding the following to php.ini:

sample4.greeting="Hello Andy"

or via command line as:

-dsample4.greeting="Hello Andy"

Expected result:
When running using CLI on Windows, i.e a ZTS enabled build, I 
expected to see 1 call to my extensions "OnModify" callback 
routine for each thread attached; so in this simple case I expected to see just the 1 call as follows:

>> sample 4: thread 0xfbc minit
sample 4: thread 0xfbc greeting value is Hello Andy
<< sample 4: thread 0xfbc minit
Hello Andy

Actual result:
The OnModify call back routine is in fact called 3 times; once
during MINIT processing and twice further. These last 2 are during the call to zend_new_thread-end_handler().

>> sample 4: thread 0x16f8 minit
sample 4: thread 0x16f8 greeting value is Hello Andy
<< sample 4: thread 0x16f8 minit
sample 4: thread 0x16f8 greeting value is Hello Andy
sample 4: thread 0x16f8 greeting value is Hello Andy
Hello Andy


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 [2006-11-03 09:03 UTC] wharmby at uk dot ibm dot com
Correcting version; behaviour was observed in V5 not V4
 [2006-11-08 11:05 UTC]
The patches applied to CVS HEAD and PHP_5_2.
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