Edit report at http://bugs.php.net/bug.php?id=51552&edit=1
ID: 51552
Updated by: tony2...@php.net
Reported by: kkotowicz at gmail dot com
Summary: debug_backtrace() causes segmentation fault and/or
memory issues
-Status: Open
+Status: Assigned
Type: Bug
Package: Reproducible crash
Operating System: win/linux
PHP Version: 5.3.2
-Assigned To:
+Assigned To: dmitry
Previous Comments:
------------------------------------------------------------------------
[2010-04-29 18:44:47] kkotowicz at gmail dot com
I dug depper into the issue, it looks as debug_backtrace() and functions
accepting references are causing the problem.
Here's the script that describes it:
<?php
function walk($element, $key, $p) {
var_dump(func_get_args());
$backtrace = debug_backtrace();
//var_dump($backtrace);
unset($backtrace); // commenting this line crashes PHP
}
$a = range(1,10);
array_walk($a, 'walk', 'testthis');
?>
this results in:
array(3) {
[0]=>
int(1)
[1]=>
int(0)
[2]=>
string(8) "testthis"
}
array(3) {
[0]=>
int(2)
[1]=>
int(1)
[2]=>
string(8) "! 1 "
}
array(3) {
[0]=>
int(3)
[1]=>
int(2)
[2]=>
int(2)
}
array(3) {
[0]=>
int(4)
[1]=>
int(3)
[2]=>
string(4) "! "
}
Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to
allocate
134217728 bytes) in E:\tmp\php_bug\bug.php on line 4
for the first iteration, everything is ok. But each next time walk() is
called, the $p argument gets some random value, thus pointing to the
memory issues with debug_backtrace(). The backtrace itself will show
some garbage each next time.
------------------------------------------------------------------------
[2010-04-28 19:40:08] kkotowicz at gmail dot com
The same problem occurs when running php 5.3.2/Win32
Backtrace generated from MS Debug Diagnostic Tool below:
Entry point php!mainCRTStartup
Create time 2010-04-28 19:34:00
Time spent in user mode 0 Days 0:0:0.15
Time spent in kernel mode 0 Days 0:0:0.0
Function Arg 1 Arg 2 Arg 3 Source
php5!zend_hash_num_elements+4 00000000 00000000 1007dbc0
php5!_zval_copy_ctor_func+61 01170378 011a0080 01170a50
php5!zend_startup_builtin_functions+2b54 00000000 01171648
011a0278
php5!zend_fetch_debug_backtrace+21a 01170830 00c0ea4c
00000001
php5!zend_fetch_debug_backtrace+374 00000000 01170830
00000000
php5!execute+cdf 011a0278 01172d68 011a0278
php5!execute+4c25 00000000 10549738 10544688
php5!execute+1f0 0129cb18 0116f5f0 00c0eb30
php5!zend_call_function+6c1 10544688 105446ac 00c0eb70
php5!zif_max+3d3 0116f5f0 00c0eb30 00000000
php5!zif_array_walk+cf 00000003 01170260 00000000
php5!execute+cdf 011a0080 0116f668 011a0080
php5!execute+4c25 00c0ec28 00c0fed4 00c0fcbc
php5!execute+1f0 0116f668 00c0fed4 00000000
php5!zend_execute_scripts+be 00000008 00000000 00000003
php5!php_execute_script+1e2 00c0fed4 0040642c 00000001
php!main+a9a 00000004 003d31d0 003d3450
php!memcpy+160 0000000e 00000000 7ffdf000
kernel32!BaseProcessStart+23 00402dda 00000000 00000000
PHP5!ZEND_HASH_NUM_ELEMENTS+4In
php__PID__2516__Date__04_28_2010__Time_07_34_10PM__865__Second_Chance_Exception_C0000005.dmp
the assembly instruction at php5!zend_hash_num_elements+4 in
E:\tmp\php_bug\bin\php5.dll from The PHP Group has caused an access
violation exception (0xC0000005) when trying to read from memory
location 0x00000008 on thread 0
------------------------------------------------------------------------
[2010-04-28 18:30:03] kkotowicz at gmail dot com
gdb backtrace for the failing script below:
#0 zend_hash_num_elements (ht=0x868f630) at
/home/xxx/debugPHP/php-5.3.2/Zend/zend_hash.c:1014
#1 0x082b6665 in debug_backtrace_get_args (curpos=<value optimized
out>)
at /home/xxx/debugPHP/php-5.3.2/Zend/zend_variables.h:45
#2 0x082b68a2 in zend_fetch_debug_backtrace (return_value=0x868f854,
skip_last=1, provide_object=1)
at /home/xxx/debugPHP/php-5.3.2/Zend/zend_builtin_functions.c:2195
#3 0x082b6b44 in zif_debug_backtrace (ht=0, return_value=0x868f854,
return_value_ptr=0x0, this_ptr=0x0,
return_value_used=1) at
/home/xxx/debugPHP/php-5.3.2/Zend/zend_builtin_functions.c:2269
#4 0x082ec629 in zend_do_fcall_common_helper_SPEC
(execute_data=0x86bffa4)
at /home/xxx/debugPHP/php-5.3.2/Zend/zend_vm_execute.h:313
#5 0x082c6540 in execute (op_array=0x869036c) at
/home/xxx/debugPHP/php-5.3.2/Zend/zend_vm_execute.h:104
#6 0x0829a77a in zend_call_function (fci=0x85c9348,
fci_cache=0x85c936c)
at /home/xxx/debugPHP/php-5.3.2/Zend/zend_execute_API.c:947
#7 0x081efdd8 in php_array_walk (target_hash=0x868d824,
userdata=0xbfc3d704, recursive=0)
at /home/xxx/debugPHP/php-5.3.2/ext/standard/array.c:1109
#8 0x081f035f in zif_array_walk (ht=3, return_value=0x868de00,
return_value_ptr=0x0, this_ptr=0x0,
return_value_used=0) at
/home/xxx/debugPHP/php-5.3.2/ext/standard/array.c:1151
#9 0x082ec629 in zend_do_fcall_common_helper_SPEC
(execute_data=0x86bfe10)
at /home/xxx/debugPHP/php-5.3.2/Zend/zend_vm_execute.h:313
#10 0x082c6540 in execute (op_array=0x868d78c) at
/home/xxx/debugPHP/php-5.3.2/Zend/zend_vm_execute.h:104
#11 0x082a4cd4 in zend_execute_scripts (type=8, retval=0x0,
file_count=3)
at /home/xxx/debugPHP/php-5.3.2/Zend/zend.c:1194
#12 0x08252928 in php_execute_script (primary_file=0xbfc3fb88) at
/home/xxx/debugPHP/php-5.3.2/main/main.c:2260
#13 0x08324976 in main (argc=2, argv=0xbfc3fce4) at
/home/xxx/debugPHP/php-5.3.2/sapi/cli/php_cli.c:1192
------------------------------------------------------------------------
[2010-04-28 17:42:00] kkotowicz at gmail dot com
I tried compiling PHP 5.3.2 and noticed that when compiling with
--enable-debug the error disappears (no segmentation fault). Exact
configure line is:
# ./configure --disable-xml --disable-libxml --disable-simplexml
--disable-xmlreader --disable-xmlwriter --disable-dom --without-pear
--enable-debug
Standard compilation without debugging symbols:
# ./configure --disable-xml --disable-libxml --disable-simplexml
--disable-xmlreader --disable-xmlwriter --disable-dom --without-pear
and the error (I lack gdb skills so I don't know what to report more)
r...@xxx:/home/xxx/debugPHP/php-5.3.2/sapi/cli# gdb --args ./php
bug.php
GNU gdb 6.8-debian
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show
copying"
and "show warranty" for details.
This GDB was configured as "i486-linux-gnu"...
(gdb) run
Starting program: /home/xxx/debugPHP/php-5.3.2/sapi/cli/php bug.php
[Thread debugging using libthread_db enabled]
[New Thread 0xb7d116b0 (LWP 1627)]
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb7d116b0 (LWP 1627)]
zend_hash_num_elements (ht=0x868f630) at
/home/xxx/debugPHP/php-5.3.2/Zend/zend_hash.c:1014
1014 {
------------------------------------------------------------------------
[2010-04-23 19:13:12] fel...@php.net
It doesn't crash for me, but the Valgrind points actually memory issues
(invalid write/read, and so on):
[...]
==25121== ERROR SUMMARY: 16 errors from 16 contexts (suppressed: 90 from
3)
==25121== malloc/free: in use at exit: 3,673 bytes in 76 blocks.
==25121== malloc/free: 30,671 allocs, 30,595 frees, 3,020,064 bytes
allocated.
==25121== For counts of detected errors, rerun with: -v
==25121== searching for pointers to 76 not-freed blocks.
==25121== checked 1,007,216 bytes.
==25121==
------------------------------------------------------------------------
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