When using OdCopyEx.cpp to convert the CAD file version, the out of memory dialog box pops up, and the code throws an exception when readFile.

Dwg file format is highly compressed and drawing occupied much more memory than file size.
Memory limit for 32-bit application is 2G. 64-bit application has no such limitation.
In some scenarios partial loading and paging can reduce memory usage but saving drawing to file require that all data is loaded into memory.