[Python-Dev] Stackless Python (original) (raw)

Bob Ippolito bob at redivi.com
Mon May 31 17:39:01 EDT 2004

On May 31, 2004, at 5:25 PM, Martin v. Löwis wrote:

Bob Ippolito wrote:

I'm believe that map and filter are non-recursive Can you point me to the code that demonstrates this? Looking at Stackless' src/Python/bltinmodule.c:builtinmap, I see for (i = 0; ; ++i) { ... value = PyEvalCallObject(func, alist); ... PyListSetItem(result, i, value) ... } which looks recursive to me.

Ok, then I am mistaken. I thought I had seen a commit message that said it was made non-recursive. Either way, it's possible to write a non-recursive version of map or anything else, it's just a bit of work.

I am not sure about unicode encode/decode. I don't think it's very common to do a tasklet switch in the middle of a unicode encode or decode, though :) I thought Stackless was not only about tasklet switching, but also about running without stack... Wouldn't it perform the "hard" switching if the stack is running too deep?

I don't think so, because the C stack should never run too deep, since most code that is going to recurse (from the python-view) will do it non-recursively (from the C-view).

Py-func1() -> C-func1() -> Py-func2() -> switch to new tasklet Py-func3() -> C-func2() -> throw exception() I don't see how it could cause problems unless this is valid: PyFunc1 -> CPlusPlusExceptionCatcher -> PyFunc2 -> CPlusPlusExceptionThrower -> throws exception() It crashes in the process of throwing the exception - not because it finds no exception handler. It crashes because the internal data structures have been corrupted. I should have better made this example: Py-func1() -> C-func1() -> Py-func2() -> switch to new tasklet Py-func3() -> Exception-Catcher -> C-func2() -> throw exception() If that is valid, how the heck does PyFunc2 get cleaned up? I have to admit that I'm not very familiar with C++'s implementation of exceptions. Throwing exceptions through Python functions is not supported, indeed. However, I was trying to point out that the entire exception handling mechanism gets corrupted, even if there are valid handlers on the stack.

I don't think that the entire exception handling mechanism gets corrupted. Each tasklet should always have a consistent view of the C stack. Anyway, I don't think we need to discuss it any further unless someone writes a failing test... and if that is indeed the case, then the discussion should be taken to the stackless list.

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