Bug 11008 – Allow -main switch even if user-defined main function exists

Currently, if user-defined main() function exists, specifying -main switch will fail to compile. // test.d void main() {} $ dmd -main -run test test.d(1): Error: only one main/WinMain/DllMain allowed, -main switch added another main() But I think this is unnecessary restriction. Compiler can stop adding "another main" when user-defined main() detected.

It could also be argued that it's misleading if -main works when there's already a main function, because instead of simply running the unit tests, the main is going to do whatever the already included main function does. Giving the user an error alerts them to the fact that they're trying to add a main when there already is one (one which almost certainly doesn't do what they want). So, it seems to me that not having -main error out gains us little and causes problems when someone tries to use -main when they already have a main function defined.

Ok. I withdraw this.

One way to do this is to introduce separate option, say -fno-main-error which does what was proposed in this enh without screwing current switch.

(In reply to comment #3) > One way to do this is to introduce separate option, say -fno-main-error which > does what was proposed in this enh without screwing current switch. (In reply to comment #3) > One way to do this is to introduce separate option, say -fno-main-error which > does what was proposed in this enh without screwing current switch. something more general and useful would be: dmd -main=mypck.mymodule.myfunction [...] which specifies the main function to use.

What about something like -emptymain to actually force an empty main function to replace an optionally existing one. That way you'd be be able to run the unittests without executing anything else?

I'm reopening, since it is useful to have the `-main` switch replace the user-defined function given that the default druntime behavior is to not run `main()` after executing unit tests, since dmd 2.090 - https://dlang.org/changelog/2.090.0.html#unittest-default | https://run.dlang.io/is/GzX7qt Currently, running `dub test --single` fails if there's a user-defined main: https://github.com/dlang/dub/issues/2122, because of this behavior.

Also, if it is deemed that this would be a breaking change, than I suggest we go with Rainer's suggestion for `-emptymain`.

@ZombieDev As a heads up, following [1], the following code in run.dlang.org [2] produces the only one main error due to relying on dub test --single. ```d /+dub.sdl: dependency "mir-algorithm" version="*" +/ import core.stdc.stdio; unittest { printf("From unittest\n"); } void main() { printf("From main\n"); } ``` [1] https://github.com/dlang-tour/core-exec/pull/56 [2] https://run.dlang.io/is/0PlIZU

@dkorpel created dlang/dmd pull request #13057 "Fix issue 11008 - Allow -main switch even if user-defined main function exists" fixing this issue: - fix issue 11008 - Allow -main switch even if user-defined main function exists https://github.com/dlang/dmd/pull/13057

dlang/dmd pull request #13057 "Fix issue 11008 - Allow -main switch even if user-defined main function exists" was merged into master: - c4fa7709ee2bc93bbf071335bfb7027ea3eaf527 by dkorpel: fix issue 11008 - Allow -main switch even if user-defined main function exists https://github.com/dlang/dmd/pull/13057