Topic: Why my php extension crashed with stack overflow?

[kimryo]

My php extension just invoked several functions exported by a regular DLL,for most functions in those exported invoked,my php extension just works well,but when invoke a function which require a comparatively large memory(about less than 30M memory taken),my httpd.exe crashed with a stack overflow reason.And the function itself is ok to invoke by other applications like VB client etc.
My php is integrated with Apache as a module.Is here any memory limitation on addon modules?

My env is,Apache 2.2.6,Php 5.2.5,Windows XP SP2,Administrator account;

Any suggestion is appreciate.

[kimryo]

I've tried just now with replacing Apache to IIS,and it is ok to run my php extension,what's wrong with Apache? Could any one tell?Thanks in advance.

[tdonovan]

Unfortunately a vague description like "functions exported by a regular DLL" is not nearly enough to to reproduce your problem, or to diagnose it.

In general - Apache imposes no memory limitations on modules.
Most stack overflows on Windows are caused by a function calling itself recursively - but other causes are possible.

-tom-

[kimryo]

[tdonovan]

re: "I've wrote a library in C++ to process images..."

Maybe you are putting very large data (for example, image data) into local variables which use the stack, instead of using heap variables (new/delete in C++).
You can often get away with this mistake in single-threaded stand-alone programs, but it can cause problems in multi-threaded server programs like Apache.

Two things you can try:

1. - Use the EDITBIN program to increase the size of the stack in httpd.exe

Code:

EDITBIN /STACK:0x500000,0x10000 httpd.exe


2. - Use an Apache module like mod_fcgid or mod_fastcgi to run PHP in an external process (like IIS does), rather than running PHP inside the Apache process.

If either of these things correct the problem, it is an indication that your library does indeed use an excessive amount of stack space.
In this case, it would be better to change your code to put large data into heap space rather than stack space.

-tom-

[kimryo]