[New-bugs-announce] [issue26287] Core dump in f-string with lambda and format specification

[Petr Viktorin]

New submission from Petr Viktorin:

Evaluating the expression f"{(lambda: 0):x}" crashes Python.

$ ./python
Python 3.6.0a0 (default, Feb  5 2016, 02:14:48) 
[GCC 5.3.1 20151207 (Red Hat 5.3.1-2)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> f"{(lambda: 0):x}"  
Fatal Python error: Python/ceval.c:3576 object at 0x7f6b42f21338 has negative ref count -2604246222170760230
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: non-empty format string passed to object.__format__
Aborted (core dumped)

----------
messages: 259609
nosy: encukou, eric.smith
priority: normal
severity: normal
status: open
title: Core dump in f-string with lambda and format specification
versions: Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue26287>
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