When I tried to open a 1gb DWG file using cadlib, I always failed. The problem is because cadlib doesn't support such large files, or because my computer is badly configured

I don't know where the exact limits are, but I will say that 1 GB is excessive and I won't spend any effort on investigating this. - Wout

I agree with Wout that 1GB for a DWG is a lot. That's more than 3 times what I've seen so far. Depending on the content Cadlib might need a lot more memory to display the DWG, so my guess would be that memory is the restriction here. There's no point in Cadlib where there is a check for too large file size, it just reads what it encounters. So you probably run into some resource restriction, and as said physical memory is the best bet. But without the actual DWG that is hard to find out for us what limit you are hitting. - Rammi