Le 25/04/19 à 08:25, Chris Angelico a écrit :
On Thu, Apr 25, 2019 at 2:32 PM Vincent Vande Vyvre
<vincent.vande.vy...@telenet.be> wrote:
Le 24/04/19 à 19:57, MRAB a écrit :
On 2019-04-23 20:21, Vincent Vande Vyvre wrote:
Le 23/04/19 à 20:54, Chris Angelico a écrit :
Why a SystemError ?
The SystemError means that you're using the Python C API in a way that
doesn't make sense to the interpreter. You're leaving a marker saying
"hey, I need you to throw an exception" but then you're also returning
a value. You'll need to figure out where that's happening and exactly
what is being called. How are you setting up your class?
ChrisA
The syntaxe
if (!PyArg_ParseTuple(args, "s", &fname))
return NULL;
Is the usage described in the doc [*]
And without block try-except I get the good one error.
[*]
https://docs.python.org/3.5//extending/extending.html#back-to-the-example
If you look at the previous example, the function's return type is
"PyObject *".
On success it returns a reference (pointer) to an object; on error it
returns NULL.
Your function's return type is int.
In this case yes, beause it need to return the result of the command system.
But the "return 0" is a common case for an "Foo_init()"
see:
https://docs.python.org/3.5//extending/newtypes.html#adding-data-and-methods-to-the-basic-example
... And that's nothing to do with my initial question
Actually, it is a lot to do with your initial question. Notice how
there are two distinct signatures being demonstrated in the example
you linked to: those declared as returning PyObject* and those
declared as returning int. If something is meant to return an object,
then returning NULL says "hey, I set an error state, unwind the stack
and raise the exception". If it's meant to return an integer, though,
it returns -1 to give that message. See details here (second
paragraph):
https://docs.python.org/3/c-api/intro.html#exceptions
The __init__ function is defined as returning an integer:
https://docs.python.org/3/c-api/typeobj.html#c.PyTypeObject.tp_init
You're right that "return 0" is a common case; that isn't the problem.
The problem is the "return NULL", which is correct for a function that
normally returns a PyObject*, but not for one that returns an int.
That's why you're getting a SystemError - you're setting the exception
state, but then saying "hey, everything's fine, it's okay to return
None".
ChrisA
Does not change anything with PyObject *, same behaviour.
But with "static int" and "return -1;" instead of "NULL", now I have
the correct error.
So, thanks to all and sorry for the delays of my mails but it seems I'm
always moderated ...
Vincent
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