PySequence_SetItem [英] PySequence_SetItem
问题描述
以下代码非常直接来自Python / C参考手册的
部分1.2.1.1：
#include< Python.h>
int
main（无效）
{
PyObject * l，* x;
Py_Initialize（）;
l = PyList_New（3）;
x = PyInt_FromLong（1L）;
if（l == NULL || x == NULL）{
PyErr_Print（）;
退出（EXIT_FAILURE）;
}
PySequence_SetItem（l，0，x）;
Py_DECREF（x）;
Py_Finalize（）;
返回EXIT_SUCCESS;
}
不幸的是，它没有'不行。它是段错误的，并且
当
Py_DECREF宏应用于old_value时，list_ass_item（）中出现错误，
设置在699行of Objects / listobject.c
with old_value = a-> ob_item [i]; （old_value是
设置为NULL，而Py_DECREF是
应用于NULL ...繁荣！）
我我非常擅长嵌入/扩展python，
所以我不确定我是不是在做一些令人难以置信的事情
愚蠢，但它看起来像PySequence_SetItem （）
期待在所需的索引处已经有一个
项目。
我做了一些愚蠢的事情吗？
-
Bill Pursell
Bill Pursell写道：
以下代码非常直接来自
第1.2.1.1节Python / C参考手册：
#include< Python.h>
int
main（void ）
{
PyObject * l，* x;
Py_Initialize（）;
l = PyList_New（3）;
x = P. yInt_FromLong（1L）;
if（l == NULL || x == NULL）{
PyErr_Print（）;
退出（EXIT_FAILURE）;
}
PySequence_SetItem（ l，0，x）;
Py_DECREF（x）;
Py_Finalize（）;
返回EXIT_SUCCESS;
}
另请注意，如果我将调用PySequence_SetItem替换为
，问题就会消失：
PySequence_SetItem（l，0，PyInt_FromLong（1L））;
但如果我在分配x后添加Py_INCREF（x）
，问题仍然存在。 （这似乎是一件完全愚蠢的事情，但是我正在抓住
字符串......）
Bill Pursell写道：
Bill Pursell写道：
另请注意问题是如果我用以下内容替换
调用PySequence_SetItem：
PySequence_SetItem（1,0，PyInt_FromLong（1L））;
你确定吗？它应该完全没有区别。
到目前为止我的经验：
1.在调用PySequence_SetItem时崩溃
2.删除py_DECREF，s / Sequence / List / -works OK
3.添加代码来测试PyWhatever_SetItem的返回值[你应该
*总是*测试错误]，s / Sequence / Object / -PyObject_SetItem调用
返回-1，PyErr_Print - " SystemError：null参数内部
例程"
看起来像一两个bug。我会翻找一下。
干杯，
John
2006年8月16日星期三01:45:44 PM -0700，John Machin写道：
Bill Pursell写道：
Bill Pursell写道：
另请注意，如果我将调用PySequence_SetItem替换为
，问题就会消失：
PySequence_SetItem（1,0，PyInt_FromLong（1L））;
你确定吗？它应该完全没有区别。
到目前为止我的经验：
1.在调用PySequence_SetItem时崩溃
2.删除py_DECREF，s / Sequence / List / -works OK
3.添加代码来测试PyWhatever_SetItem的返回值[你应该
*总是*测试错误]，s / Sequence / Object / -PyObject_SetItem调用
返回-1，PyErr_Print - " SystemError：null参数内部
例程"
将PySequence_SetItem更改为PyList_SetItem并删除
DECREF也适用于我（PyList函数窃取引用）。我还试图将b + b设置为长度为1，仍然没有骰子。 PySequence
版本的版本低于2.4和2.5。即使将Int更改为
到字符串也会出现问题。
Yikes，我会捅更多。
-Jack
The following code is pretty much straight out of
section 1.2.1.1 of the Python/C reference manual:
#include <Python.h>
int
main(void)
{
PyObject *l, *x;
Py_Initialize();
l = PyList_New(3);
x = PyInt_FromLong(1L);
if (l == NULL || x == NULL) {
PyErr_Print();
exit (EXIT_FAILURE);
}
PySequence_SetItem(l, 0, x);
Py_DECREF(x);
Py_Finalize();
return EXIT_SUCCESS;
}
Unforunately, it doesn''t work. It segfaults, and
the error occurs in list_ass_item() when the
Py_DECREF macro is applied to old_value, which
was set at line 699 of Objects/listobject.c
with old_value = a->ob_item[i]; (old_value is
being set to NULL, and Py_DECREF is
being applied to NULL...boom!)
I''m totally new to embedding/extending python,
so I''m not sure if I''m doing something incredibly
stupid, but it certainly looks like PySequence_SetItem()
was expecting that there should already be an
item at the desired index.
Am I doing something stupid?
--
Bill Pursell
Bill Pursell wrote:The following code is pretty much straight out of
section 1.2.1.1 of the Python/C reference manual:
#include <Python.h>
int
main(void)
{
PyObject *l, *x;
Py_Initialize();
l = PyList_New(3);
x = PyInt_FromLong(1L);
if (l == NULL || x == NULL) {
PyErr_Print();
exit (EXIT_FAILURE);
}
PySequence_SetItem(l, 0, x);
Py_DECREF(x);
Py_Finalize();
return EXIT_SUCCESS;
}Also note that the problem goes away if I replace
the call to PySequence_SetItem with:
PySequence_SetItem(l, 0, PyInt_FromLong(1L));
but the problem persists if I add a Py_INCREF(x)
after the assignment of x. (Which seems like a
completely silly thing to do, but I''m grasping
at strings...)
Bill Pursell wrote:Bill Pursell wrote:
Also note that the problem goes away if I replace
the call to PySequence_SetItem with:
PySequence_SetItem(l, 0, PyInt_FromLong(1L));Are you sure? It should make absolutely no difference.
My experience so far:
1. crashes in call to PySequence_SetItem
2. removed py_DECREF, s/Sequence/List/ -works OK
3. added code to test return value from PyWhatever_SetItem [you should
*always* test for error], s/Sequence/Object/ -PyObject_SetItem call
returns -1, PyErr_Print -"SystemError: null argument to internal
routine"
Looks like a bug or two. I''ll rummage a bit more.
Cheers,
John
On Wed, Aug 16, 2006 at 01:45:44PM -0700, John Machin wrote:Bill Pursell wrote:Bill Pursell wrote:
Also note that the problem goes away if I replace
the call to PySequence_SetItem with:
PySequence_SetItem(l, 0, PyInt_FromLong(1L));
Are you sure? It should make absolutely no difference.
My experience so far:
1. crashes in call to PySequence_SetItem
2. removed py_DECREF, s/Sequence/List/ -works OK
3. added code to test return value from PyWhatever_SetItem [you should
*always* test for error], s/Sequence/Object/ -PyObject_SetItem call
returns -1, PyErr_Print -"SystemError: null argument to internal
routine"Changing the PySequence_SetItem to PyList_SetItem and dropping the
DECREF works for me too (PyList functions steal a reference). I also
tried setting the list to length 1, still no dice. The PySequence
version segs under 2.4 and 2.5. It segs even when the Int is changed
to a String.
Yikes, I''ll poke around some more.
-Jack
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