BUG: reference count leak when using THPLayout_New and THPMemoryFormat_New (static analyzer reports)

[Snape3058]

Hint 1: In function THPLayout_New and THPMemoryFormat_New, the tp_alloc method is used to allocate the memory for the PyObject to be returned. If the default allocator function is inherited, the function call will return a new reference.

Hint 2: Function PyModule_AddObject will steal a reference to the third argument only when the return value is zero.

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• In function initializeLayouts, the trigger path provided by our analyzer is as follows. (Internal Report ID: e2a925)

1. A new reference is returned from THPLayout_New and assigned to strided_layout. (refcnt = 1)
   

   pytorch/torch/csrc/utils/tensor_layouts.cpp

   Line 25 in d1bb420

   PyObject* strided_layout = THPLayout_New(at::Layout::Strided, "torch.strided");

2. Increase the refcnt. (refcnt = 2)
   

   pytorch/torch/csrc/utils/tensor_layouts.cpp

   Line 26 in d1bb420

   Py_INCREF(strided_layout);

3. An exception is thrown without decreasing the refcnt.
   

   pytorch/torch/csrc/utils/tensor_layouts.cpp

   Line 28 in d1bb420

   throw python_error();

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• In lambda expression add_memory_format in function initializeMemoryFormats, the trigger path provided by our analyzer is as follows. (Internal Report ID: 09d8df)

1. A new reference is returned from THPMemoryFormat_New and assigned to memory_format. (refcnt = 1)
   

   pytorch/torch/csrc/utils/tensor_memoryformats.cpp

   Line 32 in d1bb420

   PyObject* memory_format = THPMemoryFormat_New(format, module_name + name);

2. Increase the refcnt. (refcnt = 2)
   

   pytorch/torch/csrc/utils/tensor_memoryformats.cpp

   Line 33 in d1bb420

   Py_INCREF(memory_format);

3. Decrease the refcnt. (refcnt = 1)
   

   pytorch/torch/csrc/utils/tensor_memoryformats.cpp

   Line 35 in d1bb420

   Py_DECREF(memory_format);

4. An exception is thrown without decreasing the refcnt.
   

   pytorch/torch/csrc/utils/tensor_memoryformats.cpp

   Line 36 in d1bb420

   throw python_error();

cc @ezyang @gchanan @zou3519

[albanD]

cc @ezyang