[Python-Dev] Making python C-API thread safe (try 2)

[Skip Montanaro]

(I'm tiring rapidly of this topic.  This is my last post.)

    >> The current none_dealloc() will rightfully complain if myfunc() is
    >> called enough times, because Py_None's reference count will go to
    >> zero.
    >> 
    Harri> Yeah, but on the other hand, the application crashes less if it
    Harri> is not checked! :-)

I know you have a smiley there, however, I want the system to do its best to
crash for me and not wait until my customer has it.

    Harri> There are 2001 explicit calls to Py_INCREF(Py_None) in C API
    Harri> source code. These are unnecessary, but the implicit calls are of
    Harri> course fine.  Removing the explicit calls would make Python
    Harri> slightly faster, just about enough to compensate the required
    Harri> changes in deallocation mechanism as least.

How do you know that?  Have you tested anything yet?

    Harri> But if the reference count is negative for allocated objects,
    Harri> then you already have a bug. I mean that the count is never
    Harri> negative when the application works correctly. The object is
    Harri> already deallocated when the count reaches zero, so checking for
    Harri> negative counts is (usually) superfluous. Python gets slightly
    Harri> faster if you just remove this check (from release version).

Much of the stuff in there for reference counting is there to help you when
the application doesn't work correctly.

    >> That's as it should be, because any statically allocated object
    >> should have a reference count of at least one.

    Harri> Why? It has no meaning, because the object was never allocated,
    Harri> and it can't be deallocated.

Because it is an object.  Structurally and semantically it should behave the
same as all the other objects in the system.

    Harri> Yeah, getting closer to that I guess. But I should not be doing
    Harri> it just yet, I have other projects, but this just keeps bugging
    Harri> me.

It's your itch.  You have to be the one to scratch it.

Skip