[Numpy-discussion] Unreliable crash when converting using numpy.asarray via C buffer interface

[Friedrich Romstedt]

Hello Matti,

Am Mo., 1. Feb. 2021 um 09:46 Uhr schrieb Matti Picus <matti.picus at gmail.com>:
>
> [...]
>
> It is very hard to help you from this description. It may be a refcount
> problem, it may be a buffer protocol problem, it may be something else.

Yes, indeed!

> Typically, one would create a complete example and then pointing to the
> code (as repo or pastebin, not as an attachment to a mail here).

https://github.com/friedrichromstedt/bughunting-01

I boiled it down considerably, compared to the program where I
stumbled upon the problem.  In the abovementioned repo, you find a
Python test script in the `test/` folder.  Therein, a single `print`
statement can be used to trigger or to avoid the error.  On Linux, I
get a somewhat more precise description than just from the premature
exit on Windows: It is a segfault.

Certainly it is still asked quite much to skim through my source code,
however, I hope that I trimmed it down sufficiently.

> - Make sure you give instructions how to build your project for Linux,
> since most of the people on this list do not use windows.

The code reproducing the segfault can be compiled by `$ python3
setup.py install`, both on Windows as well as on Linux.

> - There are tools out there to analyze refcount problems. Python has
> some built-in tools for switching allocation strategies.

Can you give me some pointer about this?

> - numpy.asarray has a number of strategies to convert instances, which
> one is it using?

I've tried to read about this, but coudn't find anything.  What are
these different strategies?

Many thanks in advance,
Friedrich