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The patch adds a new test and a new executable. The executable calls
Py_Initialze() and Py_Finalize() multiple times in a row. The test also
shows that Python looses about 35 references in each round.
$ ./test_reinit
round 1
[7751 refs]
round 2
[7797 refs]
round 3
[7834 refs]
round 4
[7871 refs]
round 5
[7908 refs]
round 6
[7945 refs]
round 7
[7982 refs]
round 8
[8019 refs]
round 9
[8056 refs]
round 10
[8093 refs]

I'm not sure what the purpose of this test is. When would it pass, when
would it fail? I don't think it is a bug if a
Py_Initialize()/Py_Finalize() cycle loses references.

Martin v. Löwis wrote:
> Martin v. Löwis added the comment:
> 
> I'm not sure what the purpose of this test is. When would it pass, when
> would it fail? I don't think it is a bug if a
> Py_Initialize()/Py_Finalize() cycle loses references.
Today my attempts to fix some reference leaks related to sys.flags and
sys.float_info caused the test to fail. A single init/final cycle worked
but the second cycle broke.
The test also shows an issue in Python 3.0. The double linked reference
list is broken:
$ ./test_reinit
round 1
[24676 refs]
round 2
[25588 refs]
round 3
* ob
object : <refcnt 0 at 0x82248e8>
type : str
refcount: 0
address : 0x82248e8
* op->_ob_prev->_ob_next
object : <refcnt 0 at 0x82248e8>
type : str
refcount: 0
address : 0x82248e8
* op->_ob_next->_ob_prev
object : bytearray(b'')
type : bytearray
refcount: 1
address : 0x839ab98
Fatal Python error: UNREF invalid object
Aborted (core dumped)

Perhaps ROUNDS, CAUSE_SEGFAULT and VERBOSE could be command-line rather
than compile-time options?

I like to keep the test as simple as possible.
Here is a new file that shows Python crashes in the third Py_Finalize().

If fixed the problem with multiple reinitialization in r60477. It took
me quite some time to find the right spot.

This is still a good idea.

Quote msg83564 "This is still a good idea.", in which case shouldn't someone push this forward, failing that close as out of date?

> Quote msg83564 "This is still a good idea.", in which case shouldn't
> someone push this forward, failing that close as out of date?
Just because someone doesn't "push this forward" doesn't mean it's out of date.

See also #10914.

Antoine, is the test still required? #10914 has introduced tests for the subinterpreter.

Ah, funny. I ended up doing the same thing as you without remembering about it!