[PHP-DEV] Re: [PHP-QA] Re: [PHP-DEV] Re: [PHP-QA] RC6 ISAPI problems From: Phil Driscoll (phil <email protected>)
Date: 12/18/00

When I run the debug version of RC6 as an isapi module on NT4 SP6, I cannot
even get a simple phpinfo() page to display.
Now that I have the thing running in my VC++ debugger in what seems to be a
reliable way, I can see where things hang up. (Note that the non debug
version definitely gets past this point - as I suspect there is less (or no)
heap integrity checking.)

The problem seems to be due to a corrupt heap which comes to light in
virtual_cwd as it tries to free(cwd) immediately before the final return in
the function. The debugger reports that 'a user breakpoint has been
encountered', and when I continue from there, the code just goes round in
circles.

I can't work out whether the cwd passed to free is a dodgy pointer or the
heap itself is corrupted somehow. cwd certainly contains the null terminated
string 'C:\WINNT\system32' which should have been allocated by the strdup at
the return from virtual_getcwd_ex.

The nearest I know how to get to a stack backtrace is to manually copy out
the Context fields from the debug window:

Loads of stuff before php gets called, then:
DLLMain
php_isapi_startup
php_module_startup
php_config_ini_startup
php_init_config
php_fopen_with_path
php_fopen_and_set_opened_path
expand_filepath
virtual_get_cwd

then we are into the C runtime with
free
_free_dbg
_free_dbg_lk
_CrtlsValidHeapPointer

then into the Kernel (no debug symbols here - just memory locations
KERNEL32! (memory location)
NTDLL! (memory location)
NTDLL! (memory location)

So, does anyone have any suggestions as to where I should go from here?

Cheers 

--
Phil Driscoll
Dial Solutions
+44 (0)113 294 5112
http://www.dialsolutions.com
http://www.dtonline.org

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