Actually the message quoted complains about the lack of _main not main, so the rest of this post is a huge overinterpretation. _main is IMO some windoizm connected to the use of WinMain for GUI apps.
A C program starts at the function "main", what you're discussing here is beyond the scope of the C language. C without the libc or any other form of runtime is not standard C.
I'm not trying to nitpick but I'm worried newcomers to the language might be misled by your comments, the things you're talking about are not a concern for most coders unless they have to do things like low level embedded code, bootloaders and things like that. And then your entrypoint won't be "start" anyway, it'll be the reset vector or some lower stage jumping to a specific address for instance.
Sure, I'm only trying to criticize the idea of learning language from error messages triggered by invalid (due to standards) input, as they directly take you to implementation details and other dirty stuff.
