sip - returning a MemoryView in %ConvertFromTypeCode

Scott Talbert swt at
Sun Dec 26 21:47:50 GMT 2021


I'm trying to fix a bug in wxPython where a MemoryView is returned in a 

The code is this:
PyObject* i_wxPyMakeBuffer(void* ptr, Py_ssize_t len, bool readOnly=false) 
     wxPyThreadBlocker blocker;
     if (ptr && len) {
         Py_buffer view;
         int flags = PyBUF_FORMAT|PyBUF_ND;
         if (!readOnly)
             flags |= PyBUF_WRITABLE;
         PyBuffer_FillInfo(&view, NULL, ptr, len, readOnly ? 1:0, flags);
         return PyMemoryView_FromBuffer(&view);
     } else {
         Py_INCREF(Py_None); return Py_None;

     return wxPyMakeBuffer(sipCpp->GetData(), sipCpp->GetDataLen());

This "works" but the problem is that after %ConvertFromTypeCode runs, the 
C++ object goes away, and since the MemoryView still references data from 
the C++ object, this leads to accessing memory that has been freed.  Is 
there a recommended way to handle such a situation with sip?  Ie, keep the 
C++ object around after a %ConvertFromTypeCode?  Of course, I could copy 
the all the data in %ConvertFromTypeCode, but that's the thing we're 
trying to avoid by using the MemoryView.


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