Author yselivanov
Recipients georg.brandl, gvanrossum, larry, ncoghlan, oconnor663, pitrou, serhiy.storchaka, vstinner, yselivanov
Date 2015-12-02.19:41:55
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> Should we do the same for __cause__? Is it possible to create __context__ or __cause__ loop without assigning these attributes directly?

Yes, let's mirror the __context__ behaviour for __cause__.  New patch attached.

Serhiy, Guido,

The new patch raises a TypeError in __cause__ and __context__ setters when a cycle was introduced, so in pure Python the following won't work:

   # will throw TypeError("cycle in exception context chain")
   ex.__context__ = ex chain")

   # will throw TypeError("cycle in exception cause chain")
   ex.__cause__ = ex

However, since PyException_SetContext and PyException_SetCause are public APIs, and their return type is 'void', I can't raise an error when a C code introduces a cycle, in that case, the exc->cause/exc->context will be set to NULL.


I think that this approach is the only sane one here.  We can certainly fix the infinite loop in PyErr_SetObject, but it will only be a matter of time until we discover a similar loop somewhere else.
Date User Action Args
2015-12-02 19:41:55yselivanovsetrecipients: + yselivanov, gvanrossum, georg.brandl, ncoghlan, pitrou, vstinner, larry, serhiy.storchaka, oconnor663
2015-12-02 19:41:55yselivanovsetmessageid: <>
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