New issue 3002: Some way to run "enough" gc for test suites that need to make sure destructors have run https://bitbucket.org/pypy/pypy/issues/3002/some-way-to-run-enough-gc-for-test-suites
Nathaniel Smith: It turns out that sometimes in test suites you need to pump the garbage collector manually. For example, to test a `__del__` method, you might create an object, drop the reference to it, and then do some kind of check that whatever the `__del__` method was supposed to do has actually happened. In CPython, you can usually just call `gc.collect` once and you're good. But in pypy this requires calling `gc.collect` multiple times. (No-one's sure exactly how many. I guess in principle pypy might require arbitrarily many calls to match CPython's behavior, if there's a long chain of non-cyclic garbage with destructors?) A number of projects have hit this and had to implement workarounds. For example: * https://github.com/numpy/numpy/pull/12594#discussion_r276077803 * https://github.com/python-trio/trio/blob/5aab6b56eb53bb0ce3b3002a239f8c6db36c4ff7/trio/_core/tests/tutil.py#L40-L51 It would be nice if there were a better solution than calling `gc.collect()` repeatedly until you stop getting test failures, and if each project didn't have to figure this out from scratch. It would be even nicer if `gc.collect()` just did this, so that people wouldn't have to implement workarounds when porting to pypy :-). But if you need to make it something slightly different, that's OK too. Extra points for making it compatible with CPython, like using the `gc.collect(generation=...)` argument or something. _______________________________________________ pypy-issue mailing list pypy-issue@python.org https://mail.python.org/mailman/listinfo/pypy-issue
