[pypy-issue] Issue #2798: Creating a global-variable PyObject in a C++ extension crashes while dlopening (pypy/pypy)

Hrvoje Nikšić issues-reply at bitbucket.org
Mon Apr 16 15:22:01 EDT 2018


New issue 2798: Creating a global-variable PyObject in a C++ extension crashes while dlopening
https://bitbucket.org/pypy/pypy/issues/2798/creating-a-global-variable-pyobject-in-a-c

Hrvoje Nikšić:

The attached module crashes when compiled and imported from pypy 5.10.0.

The crash is apparently triggered by global variable initialization:

```
#!c++

// global variable - crash goes away without it
PyObject *global = PyInt_FromLong(42);
```

This kind of global initialization is frequently used in our in-house CPython C++ extensions[1]. It is safe for dynamically loaded extensions because by the time the shared object gets dlopen-ed, Python has been initialized and the GIL acquired. In PyPy 5.10.0 it consistently crashes before executing the module initialization function.

Is this a bug in cpyext, or is the above pattern forbidden? Is there a workaround to make it work?

[1]
The example is, of course, simplified - in actual code, the object would be a RAII wrapper object whose constructor invokes PyInt_FromLong. It is used in many different extensions and cannot be easily replaced with, say, a function that lazily constructs and returns an object.




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