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Date: Mon, 18 Oct 2004 21:05:17 +0200
Reply-To: Marcus Boerger <helly@php.net>
Message-ID: <1533753189.20041018210517@marcus-boerger.de>
To: Zeev Suraski <zeev@zend.com>
CC: Kamesh Jayachandran <kameshj@fastmail.fm>,
  internals@lists.php.net, zeev@php.net
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Subject: Re: [PHP-DEV] why to call php_output_activate(TSRMLS_C) from php_module_startup(reposting first time)(bug #30397)
From: helly@php.net (Marcus Boerger)

Hello Zeev,

Monday, October 18, 2004, 11:14:20 AM, you wrote:

> At 08:52 18/10/2004, Kamesh Jayachandran wrote:
>>Can someone respoond to this.
>>
>>With regards
>>Kamesh Jayachandran
>>On Thu, 07 Oct 2004 23:10:24 -0700, "Kamesh Jayachandran"
>><kameshj@fastmail.fm> said:
>> > Hi All,
>> > I could see php_output_activate(TSRMLS_C) getting called from
>> > php_module_startup immedeately after php_output_startup.
>> >
>> > Why is this needed? As each SAPI modules call
>> > php_output_activate(TSRMLS_C) explicitly as a part of request startup.
>> >
>> > Why am I concerned about this?
>> >
>> > Ans: php_output_activate(TSRMLS_C) sets
>> > OG(php_body_write) = php_ub_body_write;
>> > which causes calls to php_printf to use php_ub_body_write which depends
>> > on SG(request_info) which is null while php_printf is invoked as part of
>> > apache startup error(Like Invalid extension/ Non existent extension)
>> > logging.
>> >
>> > This causes segmentation fault.
>> >
>> > This change seems to have been introduced in version 1.371 of
>> > main/main.c by Zeev(3 years and 3 months ago).
>> > The comment says,
>> > Fix a major thread safety bug in the output mechanism
>> > @- Fixed a major memory corruption bug in the thread safe version (Zeev)
>> > Can I remove a call to php_output_activate(TSRMLS_C) from
>> > php_module_startup?
>> >

> Actually this existed beforehand, the change just shifted code around (the
> point of this commit was actually NOT to call php_output_startup() on every
> request startup, and it introduced php_output_activate() which is the one 
> being called on every request startup instead).
>  From looking at the source code it appears that the call to 
> php_output_activate() during php_module_startup() was added to keep 
> 'compatibility' with the code prior to this commit.  It looks that this 
> commit fixed the main problem but kept a minor one.  I *think* it can be 
> safely removed.

>> > PS:What is the use of display_startup_errors? What does display mean
>> > with respect to startup as it might not have any associated request
>> > context?

> It has to do with errors that happen during request startup (such as file 
> upload related errors) which cannot be trapped in userland.  The check 
> currently present php_error_cb() appears to be messy, though - it should 
> probably be fixed to be just:
> if (PG(display_errors)
>          && module_initialized
>          && (!PG(during_request_startup) || PG(display_startup_errors)) {

> This messiness may be related to the other issue you mentioned.

We also know of a few bug reports that might have their origin here.
In the past i tried to fix all situations i could detect and replicate
however there might be others since the code has changed a lot.


Best regards,
 Marcus                            mailto:helly@php.net