remove obsolete extern declaration of main()

[WalterBright]

That extern declaration was causing the Mac linker to error out. And it took me a while to figure out where the extra declaration was coming from.

[rikkimax]

Given that this was working for x86, this smells, and it does seem odd that multiple externs are resulting in an error.

[WalterBright]

The linker for the other platforms will merge the duplicates. The linker for Arm64 does not. I cannot fix the linker.

[rikkimax]

Have you confirmed that with clang?

It could be something on our end with flags.

[WalterBright]

Have you confirmed that with clang?

? I use the Mac clang ld linker, which dies when it sees two declarations with the same name. Chatgpt also told me that it was broken to have such. I can't fix the linker, I have to live with it.

Eliminating the duplicate in the code generation is a good solution.

There's another one I have to eliminate - the _Dmain duplication, which is turning out to be a bit harder to remove. core.internal.entrypoint is the culprit on that one.

Please merge this so I can move on with fixing the _Dmain problem.

[rikkimax]

I am meaning to use clang with source files to generate multiple declarations, does it differ from the object file dmd is generating?

Please confirm, it could be hiding a different bug in dmd, if clang does the same then yeah I'll merge it.

[WalterBright]

If you make multiple declarations of the same name in the same object file, it will work with x86_64, but not with Arm64.

[WalterBright]

thank you!

[rikkimax]

thank you!

Now you get one :P

#23314