Please try using this CVS snapshot:

  http://snaps.php.net/php5.2-latest.tar.gz
 
For Windows (zip):
 
  http://snaps.php.net/win32/php5.2-win32-latest.zip

For Windows (installer):

  http://snaps.php.net/win32/php5.2-win32-installer-latest.msi

I've tried both PHP 5.2 and 5.3 and cannot reproduce the crash.

PHP 5.2.5RC2-dev (cli) (built: Oct 29 2007 21:22:10):

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1211684448 (LWP 31245)]
zend_lookup_class_ex (name=0xb722e018 'a' <repeats 200 times>..., 
    name_length=10000000, use_autoload=0, ce=0xbfa0c498)
    at /home/felipe/php5.2-200710292130/Zend/zend_execute_API.c:1046
1046            zend_str_tolower_copy(lc_name, name, name_length);

Always reproducible on linux64 bit hosts.

Segfaults for me too, looks like a stack smash with valgrind:


==7344== Warning: client switching stacks?  SP change: 0x7FEFFD9A0 --> 0x7FE674310
==7344==          to suppress, use: --max-stackframe=10000016 or greater
==7344== Invalid write of size 8
==7344==    at 0x85D4D3: zend_lookup_class_ex (zend_execute_API.c:1046)
==7344==  Address 0x7FE674308 is on thread 1's stack
==7344== 
==7344== Process terminating with default action of signal 11 (SIGSEGV)
==7344==  Access not within mapped region at address 0x7FE674308
==7344==    at 0x85D4D3: zend_lookup_class_ex (zend_execute_API.c:1046)
==7344== 
==7344== Invalid write of size 8
==7344==    at 0x4A1E310: _vgnU_freeres (vg_preloaded.c:56)
==7344==  Address 0x7FE674300 is on thread 1's stack
==7344== 
==7344== Process terminating with default action of signal 11 (SIGSEGV)
==7344==  Access not within mapped region at address 0x7FE674300

Which makes sense, as lc_name in 
zend_lookup_class_ex() is allocated on line 1045 with:

    lc_name = do_alloca(name_length + 1);
    zend_str_tolower_copy(lc_name, name, name_length);

SPL and Reflection have the same problem in the files:

ext/spl/php_spl.c
ext/reflection/php_reflection.c

A possible fix would be to set an arbitrary limit on the name of classes here...

Index: Zend/zend_execute_API.c
===================================================================
RCS file: /repository/ZendEngine2/zend_execute_API.c,v
retrieving revision 1.331.2.20.2.24.2.8
diff -u -p -r1.331.2.20.2.24.2.8 zend_execute_API.c
--- Zend/zend_execute_API.c     7 Oct 2007 05:22:03 -0000       1.331.2.20.2.24.2.8
+++ Zend/zend_execute_API.c     30 Oct 2007 10:14:29 -0000
@@ -1073,6 +1073,10 @@ ZEND_API int zend_lookup_class_ex(const
        if (name == NULL || !name_length) {
                return FAILURE;
        }
+
+       if(name_length >= ZEND_MAX_CLASSNAME_LEN) {
+               zend_error(E_ERROR, "Class name cannot be longer than %d", ZEND_MAX_CLASSNAME_LEN);
+       }

        lc_free = lc_name = do_alloca(name_length + 1);
        zend_str_tolower_copy(lc_name, name, name_length);
Index: Zend/zend.h
===================================================================
RCS file: /repository/ZendEngine2/zend.h,v
retrieving revision 1.293.2.11.2.9.2.7
diff -u -p -r1.293.2.11.2.9.2.7 zend.h
--- Zend/zend.h 7 Oct 2007 05:22:02 -0000       1.293.2.11.2.9.2.7
+++ Zend/zend.h 30 Oct 2007 10:14:29 -0000
@@ -712,7 +712,7 @@ END_EXTERN_C()


 #define ZEND_MAX_RESERVED_RESOURCES    4
-
+#define ZEND_MAX_CLASSNAME_LEN                 65535
 #include "zend_operators.h"
 #include "zend_variables.h"


ZEND_MAX_CLASSNAME_LEN being the same as java, not to mention that I dont see any reason why such insane long naming will be useful :-)

HTH.

That would already allocate 64kb on the stack, I doubt that will work on all systems. I would suggest a somewhat smaller limit, say 1024?

Yes, an smaller limit like 1024 looks OK and is still high enough to avoid annoying insane coders ;-)

The suggested patch is going to fix only one place, however the same stack overflow may be reached using several other places which use do_alloca(). I'll try to think about general solution.

See also bug #43298

Fixed in CVS HEAD and PHP_5_3.

Fixed in PHP_5_2 too.