[New-bugs-announce] [issue24606] segfault caused by nested calls to map()

David Lukeš report at bugs.python.org
Fri Jul 10 17:50:22 CEST 2015

New submission from David Lukeš:

The following program makes Python 3.4.3 crash with a segmentation fault:

#!/usr/bin/env python3

import operator

N = 500000
l = [0]

for i in range(N):
    l = map(operator.add, l, [1])


I suppose the problem is that there are too many nested lazy calls to map, which cause a segfault when evaluated. I've played with N and surprisingly, the threshold to cause the crash varied slightly (between 130900 and 131000 on my machine).

I know that a list-comprehension, which is evaluated straight away, would be much more idiomatic for repeated element-wise addition (or numpy arrays for that matter, if available). I'm **not advocating this piece of code**, just wondering whether there couldn't be a more informative way to make Python bail out instead of the segfault? (In my real application, it took me a while to figure where the problem was without a stack trace.)

messages: 246567
nosy: David Lukeš
priority: normal
severity: normal
status: open
title: segfault caused by nested calls to map()
type: crash
versions: Python 3.4

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