why to call php_output_activate(TSRMLS_C) from php_module_startup View as Markdown

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?

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?

With regards
Kamesh Jayachandran

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.

Zeev