Recursive setting attributes causes IronPython crashing.

[xiaxinmeng]

The following example causes stackoverflow of IronPython

import sys

class Foo():
    def __getattr__(self, name):
        if name=='bar':
            if not hasattr(self, 'bar'):
                self.bar = 42
            return self.bar
        raise AttributeError(name)


print(Foo().bar)

Crash report:

...... at IronPython.Hosting.PythonCommandLine.Run () [0x000d8] in <5cd2739cd27844619789a1aa1ffdb0b0>:0 at Microsoft.Scripting.Hosting.Shell.CommandLine.Run (Microsoft.Scripting.Hosting.ScriptEngine engine, Microsoft.Scripting.Hosting.Shell.IConsole console, Microsoft.Scripting.Hosting.Shell.ConsoleOptions options) [0x0003c] in <252827dbc7924637ba1c8c95b5f54810>:0 at Microsoft.Scripting.Hosting.Shell.ConsoleHost.RunCommandLine () [0x00053] in <252827dbc7924637ba1c8c95b5f54810>:0 at Microsoft.Scripting.Hosting.Shell.ConsoleHost.ExecuteInternal () [0x00051] in <252827dbc7924637ba1c8c95b5f54810>:0 at PythonConsoleHost.ExecuteInternal () [0x00025] in <9cafe2448f474c41b81ba0c1d71815eb>:0 at Microsoft.Scripting.Hosting.Shell.ConsoleHost.Execute () [0x00032] in <252827dbc7924637ba1c8c95b5f54810>:0 at Microsoft.Scripting.Hosting.Shell.ConsoleHost.Run (System.String[] args) [0x0015b] in <252827dbc7924637ba1c8c95b5f54810>:0 at PythonConsoleHost.Main (System.String[] args) [0x00020] in <9cafe2448f474c41b81ba0c1d71815eb>:0

System

IronPython 3.4.0a1 (3.4.0.0001) [.NETFramework,Version=v4.6 on Mono 6.12.0.122 (64-bit)] on linux