Bug 754 - IronPython stack overflow crashes Mono
Summary: IronPython stack overflow crashes Mono
Alias: None
Product: Runtime
Classification: Mono
Component: General ()
Version: unspecified
Hardware: All All
: --- normal
Target Milestone: ---
Assignee: Bugzilla
Depends on:
Reported: 2011-09-12 08:19 UTC by Doug Blank
Modified: 2013-09-08 19:12 UTC (History)
3 users (show)

Is this bug a regression?: ---
Last known good build:

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Description Doug Blank 2011-09-12 08:19:30 UTC
If you have a stack overflow in IronPython, then it crashes all of Mono, rather than raising an Exception.


$ mono ipy.exe
IronPython 3.0 ( on .NET 2.0.50727.1433
Type "help", "copyright", "credits" or "license" for more information.
>>> def recur():
...     recur()
>>> recur()

Native stacktrace:

	mono() [0x489171]
	mono() [0x4d154f]
	/lib/x86_64-linux-gnu/libpthread.so.0(+0xfc60) [0x7f2303075c60]
	mono() [0x4d1498]
	/lib/x86_64-linux-gnu/libpthread.so.0(+0xfc60) [0x7f2303075c60]

Debug info from gdb:

Could not attach to process.  If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operation not permitted.

Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries 
used by your application.


Appears to be a problem running in all versions of Mono including up to 2.10.x. Should raise a Python exception, and continue in IronPython.
Comment 1 Zoltan Varga 2011-09-14 09:17:28 UTC
Stack overflows are difficult to recover from, so the runtime usually prints a stack trace and terminates. I get:

Stack overflow: IP: 0x407844c3, fault addr: (nil)
  at IronPython.Runtime.Operations.PythonOps.GetVariable (IronPython.Runtime.CodeContext,
string,bool) <0x0006b>
  at IronPython.Runtime.Operations.PythonOps.GetLocal (IronPython.Runtime.CodeContext,str
ing) <0x00013>
  at (wrapper dynamic-method) object.recur$2 (System.Runtime.CompilerServices.Closure,Iro
nPython.Runtime.PythonFunction) <0x000a1>
  at IronPython.Runtime.PythonFunction/FunctionCaller.Call0 (System.Runtime.CompilerServi
ces.CallSite,IronPython.Runtime.CodeContext,object) <0x000a2>
  at (wrapper dynamic-method) object.recur$2 (System.Runtime.CompilerServices.Closure,Iro
nPython.Runtime.PythonFunction) <0x000b9>

What platform is this ? What is the output of mono --version ?
Comment 2 Doug Blank 2011-09-14 09:21:20 UTC
The output here is Linux, but I will test on all OS (I believe the behavior is the same).

As I mentioned, I have tried on many versions of Mono up to 2.10. Here is the output of one system that fails:

$ mono -V
Mono JIT compiler version 2.6.7 (Debian 2.6.7-5ubuntu3)
Copyright (C) 2002-2010 Novell, Inc and Contributors. www.mono-project.com
	TLS:           __thread
	GC:            Included Boehm (with typed GC and Parallel Mark)
	SIGSEGV:       altstack
	Notifications: epoll
	Architecture:  amd64
	Disabled:      none
Comment 3 Doug Blank 2011-09-14 09:26:45 UTC
Additional information:

One should be able to try/except the stack overflow in IronPython. Thus, the stack overflow in IronPython should not be a Mono stack overflow... there should be a level that Mono can catch the stack overflow in IronPython and deal with it accordingly. 

It looks like there is a conflation between the the IronPython exception raised, and a true CLR exception.

The code does not crash IronPython when running under .NET... it just raises the IronPython exception.
Comment 4 Doug Blank 2011-09-14 11:23:32 UTC
The sample IronPython code:

def recur():

crashes on all operating systems, with all tested versions of Mono (including 2.8 on Windows, and 2.10.4 on Mac).

As far as I know, there are no known workarounds.

Please let me know if you need additional information.
Comment 5 Rodrigo Kumpera 2013-09-08 19:12:59 UTC
Mono now ship with proper stack overflow handling on all targets.