On 18/07/2006 1:45 PM, [EMAIL PROTECTED] wrote: >> Let's try reductio ad adsurdum on that one. Suppose that instead of >> filling in a malloced chunk of memory, you had stored those gizmoids in >> local variables foo0, foo1, foo2, etc. Using your reasoning: we can't >> ever return from our function (which frees up the stack memory >> containing foo0 etc) because we don't know when garbage collector will >> free foo0 etc. Avoiding that problem would require a Python/C API >> function with a name like Py_AwaitGarbageCollection() ... but there >> isn't one. > > There are 2 memory components that make up a Python object. > First, there is the object in memory itself. Secondly, there > is the 4 bytes or so that hold the address to the object in memory. > (the 'pointer')
*WRONG*. The object exists in and of itself. There may be one *or more* references to it, via pointers, scattered about in memory; they are *NOT* components of the object. A reference count is maintained inside the object and manipulated by Py_INCREF etc. The Python garbage collector knows *nothing* about the memory occupied by those pointers; it is *your* responsibility to allocate and free them. If the pointers are in a function's local variables, that memory is automatically returned when you return from the function. If the pointers are in a chunk of memory that you grabbed using malloc(), then you must free() the chunk as soon as you are finished with it. Like I said: You malloced it? You free it. You didn't malloc it? You don't free it. > > I think what I hear you saying is that garbage collection has > to automagically take care of my second component above as well. I'm terribly sorry, but there is no magic involved with memory management at this level; only hard, tedious, error-prone work. Python garbage collection has neither the responsibility nor the necessary information for carrying out that task. *YOU* have that information; it is *YOUR* responsibility. > > So can I assume you are also saying our original malloc'd pointer > to Python objects will be take care of as well as the objects? *NO* You must free() any memory that you malloc()ed. > (Hence, no free(my_array) necessary?) *NO* You must free() any memory that you malloc()ed. > (Only Py_INCREFs and Py_DECREFs need apply?) *NO* You must free() any memory that you malloc()ed. "What I tell you three times is true" -- the Bellman in "The Hunting of the Snark", by Lewis Carroll. HTH, John -- http://mail.python.org/mailman/listinfo/python-list
