The difference between traditional DLL and COM DLL

Question

I am currently studying COM. I found that COM DLL is kind of built upon the traditional DLL infrastructure. When we build COM DLLs, we still rely on the traditional DLL export m

Answer 1

No, there's a Big difference. COM has a well defined protocols for creating objects, exposing methods, managing memory, publishing type information, managing threading. There is practically no language left that doesn't support using a COM server, no matter what language it was written in.

You will not get that from exposing your own functions directly. That will likely be only usable from a program written in C/C++ (so it can read your header files), compiled with the exact same version of the C++ compiler and no lack of all kinds of interop problems. Something as simple as exposing a C++ class object like std::string is not safe. Neither the memory layout is guaranteed to be compatible, nor is there any kind of memory ownership protocol.

It could well be more OOPy, COM doesn't support inheritance because OOP is so hard to get compatible at the binary level. That problem requires runtime support that all code buys into, VMs like .NET and Java.