[Python-Dev] possible fix for recursive call segfault (original) (raw)

Armin Rigo arigo at tunes.org
Tue Apr 18 14:41:09 CEST 2006

Hi Brett,

On Mon, Apr 17, 2006 at 05:34:16PM -0700, Brett Cannon wrote:

+ if (meth == self) { + PyErrSetString(PyExcRuntimeError, + "recursive call definition"); + return NULL; + }

This is not the proper way, as it can be worked around with a pair of objects whose call point to each other. The solution is to use the counter of Py_{Enter,Leave}RecursiveCall(), as was done for old-style classes (see classobject.c).

By the way, this is a known problem: the example you show is Lib/test/crashers/infinite_rec_3.py, and the four other infinite_rec_*.py are all slightly more subtle ways to trigger a similar infinite loop in C. They point to the SF bug report at http://python.org/sf/1202533, where we discuss the problem in general. Basically, someone should try to drop many Py_{Enter,Leave}RecursiveCall() pairs in the source until all the currently-known bugs go away, and then measure if this has a noticeable performance impact.

A bientot,

Mr. 8 Of The 12 Files In That Directory

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