Copying an array of PyObject*

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1

Excuse me for the stupid question in advance.

Is it possible to copy a PyObject** objects doing

memcpy(new_objects, objects, length * sizeof(PyObject))

instead of using the classical for loop?

2

Without additional context, no. At a minimum you need to consider refcounts.

3

This is no different than assigning a PyObject* to a new pointer so if you make sure you’re upholding the normal invariants with respect to reference counting etc then you should be okay.

Some examples from the interpreter: listobject.c does this when sorting and dicts when merging keys.

1 Like
4

That assumes you meant

memcpy(new_objects, objects, length * sizeof(PyObject*))

(note the star in sizeof(PyObject*).

1 Like
5

Definitively :slight_smile:

6

Mh. Houston, I have a problem.

The original object was created using PyMem_NEW. After memcpyed, I use PyMem_FREE to remove the old object, but I get:

Debug memory block at address p=0x7efd20254400: API ‘m’
128 bytes originally requested
The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.
The 8 pad bytes at tail=0x7efd20254480 are not all FORBIDDENBYTE (0xfd):
at tail+0: 0xc0 *** OUCH
at tail+1: 0x96 *** OUCH
at tail+2: 0x18 *** OUCH
at tail+3: 0x22 *** OUCH
at tail+4: 0xfd
at tail+5: 0x7e *** OUCH
at tail+6: 0x00 *** OUCH
at tail+7: 0x00 *** OUCH
Data at p: c0 92 18 22 fd 7e 00 00 … 80 96 18 22 fd 7e 00 00

Enable tracemalloc to get the memory block allocation traceback

Fatal Python error: _PyMem_DebugRawFree: bad trailing pad byte
Python runtime state: initialized

(By the way, the array in question is ma_values of dict).