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Bug #72144 _emalloc_24 crash on recursive call
Submitted: 2016-05-03 14:30 UTC Modified: 2017-11-05 04:22 UTC
Votes:1
Avg. Score:3.0 ± 0.0
Reproduced:0 of 0 (0.0%)
From: php at abiusx dot com Assigned:
Status: No Feedback Package: *Programming Data Structures
PHP Version: 7.0.6 OS: Mac OS X 10.11
Private report: No CVE-ID: None
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 [2016-05-03 14:30 UTC] php at abiusx dot com 
Description:
------------
This bug is very hard to reproduce simplistically. It is deterministic and always happens on my PHP 7 (tested on both 7.0.5 and 7.0.6), but does not happen on PHP 5.4. PHP 7.0.6 --with-debug does not crash either.

A core-dump backtrace is available below. 

Basically a recursive function, which passes around a lot of arrays and references, is crashing, very deep in the recursive part. Adding some heavy-duty code (like serialization of the array causing the crash) makes PHP crash sooner in the recursion.

$ lldb -c /cores/core.99967
(lldb) target create --core "/cores/core.99967"
warning: (x86_64) /cores/core.99967 load command 121 LC_SEGMENT_64 has a fileoff + filesize (0x29e73000) that extends beyond the end of the file (0x29e72000), the segment will be truncated to match
warning: (x86_64) /cores/core.99967 load command 122 LC_SEGMENT_64 has a fileoff (0x29e73000) that extends beyond the end of the file (0x29e72000), ignoring this section
Core file '/cores/core.99967' (x86_64) was loaded.
(lldb) bt
* thread #1: tid = 0x0000, 0x000000010200c267 phpd`_emalloc_24 + 52, stop reason = signal SIGSTOP
  * frame #0: 0x000000010200c267 phpd`_emalloc_24 + 52
    frame #1: 0x000000010207dfe8 phpd`ZEND_SEND_REF_SPEC_VAR_HANDLER + 125
    frame #2: 0x000000010207de47 phpd`ZEND_SEND_VAR_EX_SPEC_VAR_HANDLER + 82
    frame #3: 0x0000000102069f10 phpd`execute_ex + 25
    frame #4: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #5: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #6: 0x0000000102069f10 phpd`execute_ex + 25
    frame #7: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #8: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #9: 0x0000000102069f10 phpd`execute_ex + 25
    frame #10: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #11: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #12: 0x0000000102069f10 phpd`execute_ex + 25
    frame #13: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #14: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #15: 0x0000000102069f10 phpd`execute_ex + 25
    frame #16: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #17: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #18: 0x0000000102069f10 phpd`execute_ex + 25
    frame #19: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #20: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #21: 0x0000000102069f10 phpd`execute_ex + 25
    frame #22: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #23: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #24: 0x0000000102069f10 phpd`execute_ex + 25
    frame #25: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #26: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #27: 0x0000000102069f10 phpd`execute_ex + 25
    frame #28: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #29: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #30: 0x0000000102069f10 phpd`execute_ex + 25
    frame #31: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #32: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #33: 0x0000000102069f10 phpd`execute_ex + 25
    frame #34: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #35: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #36: 0x0000000102069f10 phpd`execute_ex + 25
    frame #37: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #38: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #39: 0x0000000102069f10 phpd`execute_ex + 25
    frame #40: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #41: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #42: 0x0000000102069f10 phpd`execute_ex + 25
    frame #43: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #44: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #45: 0x0000000102069f10 phpd`execute_ex + 25
    frame #46: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #47: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #48: 0x0000000102069f10 phpd`execute_ex + 25
    frame #49: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #50: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #51: 0x0000000102069f10 phpd`execute_ex + 25
    frame #52: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #53: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #54: 0x0000000102069f10 phpd`execute_ex + 25
    frame #55: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #56: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #57: 0x0000000102069f10 phpd`execute_ex + 25
    frame #58: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #59: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #60: 0x0000000102069f10 phpd`execute_ex + 25
    frame #61: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #62: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #63: 0x0000000102069f10 phpd`execute_ex + 25
    frame #64: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #65: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #66: 0x0000000102069f10 phpd`execute_ex + 25
    frame #67: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #68: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #69: 0x0000000102069f10 phpd`execute_ex + 25
    frame #70: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #71: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #72: 0x0000000102069f10 phpd`execute_ex + 25
    frame #73: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #74: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #75: 0x0000000102069f10 phpd`execute_ex + 25
    frame #76: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #77: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #78: 0x0000000102069f10 phpd`execute_ex + 25
    frame #79: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #80: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #81: 0x0000000102069f10 phpd`execute_ex + 25
    frame #82: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #83: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #84: 0x0000000102069f10 phpd`execute_ex + 25
    frame #85: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #86: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #87: 0x0000000102069f10 phpd`execute_ex + 25
    frame #88: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #89: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #90: 0x0000000102069f10 phpd`execute_ex + 25
    frame #91: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #92: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #93: 0x0000000102069f10 phpd`execute_ex + 25
    frame #94: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #95: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #96: 0x0000000102069f10 phpd`execute_ex + 25
    frame #97: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #98: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #99: 0x0000000102069f10 phpd`execute_ex + 25
    frame #100: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #101: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #102: 0x0000000102069f10 phpd`execute_ex + 25
    frame #103: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #104: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #105: 0x0000000102069f10 phpd`execute_ex + 25
    frame #106: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #107: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #108: 0x0000000102069f10 phpd`execute_ex + 25
    frame #109: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #110: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #111: 0x0000000102069f10 phpd`execute_ex + 25
    frame #112: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #113: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #114: 0x0000000102069f10 phpd`execute_ex + 25
    frame #115: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #116: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #117: 0x0000000102069f10 phpd`execute_ex + 25
    frame #118: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #119: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #120: 0x0000000102069f10 phpd`execute_ex + 25
    frame #121: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #122: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #123: 0x0000000102069f10 phpd`execute_ex + 25
    frame #124: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #125: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #126: 0x0000000102069f10 phpd`execute_ex + 25
    frame #127: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #128: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #129: 0x0000000102069f10 phpd`execute_ex + 25
    frame #130: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #131: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #132: 0x0000000102069f10 phpd`execute_ex + 25
    frame #133: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #134: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #135: 0x0000000102069f10 phpd`execute_ex + 25
    frame #136: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #137: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #138: 0x0000000102069f10 phpd`execute_ex + 25
    frame #139: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #140: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #141: 0x0000000102069f10 phpd`execute_ex + 25
    frame #142: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #143: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #144: 0x0000000102069f10 phpd`execute_ex + 25
    frame #145: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #146: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #147: 0x0000000102069f10 phpd`execute_ex + 25
    frame #148: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #149: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #150: 0x0000000102069f10 phpd`execute_ex + 25
    frame #151: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #152: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #153: 0x0000000102069f10 phpd`execute_ex + 25
    frame #154: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #155: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #156: 0x0000000102069f10 phpd`execute_ex + 25
    frame #157: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #158: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #159: 0x0000000102069f10 phpd`execute_ex + 25
    frame #160: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #161: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #162: 0x0000000102069f10 phpd`execute_ex + 25
    frame #163: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #164: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #165: 0x0000000102069f10 phpd`execute_ex + 25
    frame #166: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #167: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #168: 0x0000000102069f10 phpd`execute_ex + 25
    frame #169: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #170: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #171: 0x0000000102069f10 phpd`execute_ex + 25
    frame #172: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #173: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #174: 0x0000000102069f10 phpd`execute_ex + 25
    frame #175: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #176: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #177: 0x0000000102069f10 phpd`execute_ex + 25
    frame #178: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #179: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #180: 0x0000000102069f10 phpd`execute_ex + 25
    frame #181: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #182: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #183: 0x0000000102069f10 phpd`execute_ex + 25
    frame #184: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #185: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #186: 0x0000000102069f10 phpd`execute_ex + 25
    frame #187: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #188: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #189: 0x0000000102069f10 phpd`execute_ex + 25
    frame #190: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #191: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #192: 0x0000000102069f10 phpd`execute_ex + 25
    frame #193: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #194: 0x000000010207cc78 phpd`ZEND_DO_FCALL_SPEC_HANDLER + 986
    frame #195: 0x0000000102069f10 phpd`execute_ex + 25
    frame #196: 0x000000010201e73d phpd`dtrace_execute_ex + 238
    frame #197: 0x000000010206a142 phpd`zend_execute + 544
    frame #198: 0x000000010202d6c2 phpd`zend_execute_scripts + 299
    frame #199: 0x0000000101fd7cc4 phpd`php_execute_script + 804
    frame #200: 0x00000001020b7aaa phpd`do_cli + 3699
    frame #201: 0x00000001020b6aaa phpd`main + 1206
    frame #202: 0x00007fff86d215ad libdyld.dylib`start + 1
(lldb)

Test script:
---------------
The code is huge and I could not simplify it by any means. It is performing a deep_copy of a huge PHP array, with a lot of references.
I can provide the code in Github if needed, it is a private repo at the moment.

The recursive function calling itself is:
function &deep_copy(&$variable,&$object_pool=[],&$zval_pool=[],$depth=0,&$id_zvals=[])

and it crashes at:

			$t=&deep_copy($variable[$k],$object_pool,$zval_pool,$depth+1,$id_zvals);


$id_zvals and $variable[$k] both cause the crash. Replacing the rest of the arguments (in call) with an empty array ($a=[]) will not prevent the crash, but replacing both $id_zvals and $variable[$k] will.

$id_zvals has 181 members, all of which are references parts of the original $variable. Memory is not exhausted, about 40 MB is used and the machine has 24 GB (PHP's memlimit is unlimited).

Expected result:
----------------
No crash.

Actual result:
--------------
Segfault

Patches

Pull Requests

History

AllCommentsChangesGit/SVN commitsRelated reports
 [2016-05-24 18:15 UTC] php at abiusx dot com 
I re-implemented the same logic as a Zend Extension. The same crash happens at the same exact point. Using USE_ZEND_ALLOC=0 this is the error:

php(21970,0x7fff75d48000) malloc: *** error for object 0x7fbc5c1ac960: pointer being freed was not allocated

This is the exact same error whether I use pure PHP code or Zend extension code to do the same thing. Seems to depend on the size of the memory being utilized by the PHP process, if it is less than a certain threshold, it doesn't crash (but then crashes a few statemenets later in the same process, when only cutting out a few Kbytes).

I am pretty certain at this point that there's an error in Zend Memory Manager, specially with regards to the way it handled zend objects in PHP 7. PHP 5+ are immune to this issue.
 [2016-05-24 18:15 UTC] php at abiusx dot com 
I re-implemented the same logic as a Zend Extension. The same crash happens at the same exact point. Using USE_ZEND_ALLOC=0 this is the error:

php(21970,0x7fff75d48000) malloc: *** error for object 0x7fbc5c1ac960: pointer being freed was not allocated

This is the exact same error whether I use pure PHP code or Zend extension code to do the same thing. Seems to depend on the size of the memory being utilized by the PHP process, if it is less than a certain threshold, it doesn't crash (but then crashes a few statemenets later in the same process, when only cutting out a few Kbytes).

I am pretty certain at this point that there's an error in Zend Memory Manager, specially with regards to the way it handled zend objects in PHP 7. PHP 5+ are immune to this issue.
 [2016-05-24 18:28 UTC] nikic@php.net 
Just to make sure: Did you check that the crash is not caused by a stack overflow? You have dtrace enabled, so stack overflows are possible with simple function calls.

You suspect a bug in the Zend MM. This can be easily verified by running the program with USE_ZEND_ALLOC=0 and seeing if the crash persists.

Should the crash still occur, try running the program under "USE_ZEND_ALLOC=0 valgrind" and see if it prints any errors.
 [2016-05-24 18:30 UTC] php at abiusx dot com 
Valgrind gives me too many false positives to be usable.
Yes, the crash does persist as I said before, so you are probably right. It's not zendMM fault.

How can I increase the stack size, or something of the sort, or have a sighandler for stack overflow? Does stack overflow correlate with the size of the ZVALs in use by the program? Cuz only their references is pushed on the stack.
 [2016-05-24 18:37 UTC] nikic@php.net 
You can control the stack size limit using "ulimit -s".

What false positives does valgrind give you? PHP is usually clean under valgrind. Or are you using something like openssl in your code (or indirectly by making HTTPS requests)?
 [2016-05-24 18:40 UTC] php at abiusx dot com 
Most of them are related to libxml. It is not from PHP, but from the dylibs used by PHP under OS X. At least 18 false positive memory leaks are reported all the time, although no access violation.

Tried with ulimit -s before, didn't effect were it crashes. I am still working on that and will report in a few minutes.

The debug-enabled PHP version I currently have built lacks many libraries needed for this code. It seems likely to be a stack issue, specially since OS X has a 64MB limit on stack, however, I can't see where such stack usage comes into play. The stack depth is less than 10 in this code, although a recursive function is in play.

Will report in a few minutes about stack modifications.
 [2016-05-24 18:44 UTC] php at abiusx dot com 
Nop, tried with 8MB, 10MB and 50MB stack sizes. All crash at the same instruction.

Interestingly, using ZendMM, the program crashes a few hundred instructions later than where it crashes under USE_ZEND_ALLOC=0. The former crashes in a recursive function, whereas the latter crashes on the emulator.

This is all with regards to extending the PHP-Emulator (https://github.com/abiusx/php-emul) to support PHP static/dynamic code analysis. The heavy part seems to be the deep_copy operation needed for concolic execution.
 [2016-05-31 17:55 UTC] php at abiusx dot com 
With PHP 7.0.7, it appears that most of the problem is solved. The only crashing thing is now a fairly complex piece of code that is executed in an object destructor, which results in the following:

------ 36.16 Running wpdb::__destruct()...
--------- 36.16.1 Found direct method wpdb::__destruct()...
--------- 36.16.2 wp-includes/wp-db.php:658
phpd(66402,0x7fff75d48000) malloc: *** error for object 0x7ffafc9a3770: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap: 6

I couldn't get any useful errors out of it even with debug version. This is run with USE_ZEND_ALLOC=0, and otherwise it would crash at the same exact point.

Both destructors that cause this also return true. I am under the impression that the interpreter state is somehow corrupt inside the destructor.
 [2016-05-31 20:46 UTC] php at abiusx dot com 
confirmed that the crash occurs when cloning and object in its own constructor, and then deleting the clone, causing the destructor to be called. Static variables are also involved in all of this. 

Was unable to isolate to a simple piece of code that reproduces this.
 [2017-10-05 12:28 UTC] nikic@php.net
-Status: Open +Status: Feedback
 [2017-10-05 12:28 UTC] nikic@php.net 
The problem from the original report seems to be resolved. Is the crash mentioned later in the comments still reproducible?
 [2017-11-05 04:22 UTC] php-bugs at lists dot php dot net 
No feedback was provided. The bug is being suspended because
we assume that you are no longer experiencing the problem.
If this is not the case and you are able to provide the
information that was requested earlier, please do so and
change the status of the bug back to "Re-Opened". Thank you.
 
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