Just tried making the `main` function `private` in a kotlin

Question

Just tried making the `main` function `private` in a kotlin file and it is still executable How does JVM access the function if it is `private` and make it executable

harry.singh · Answer

Rob Elliot · Answer

If you copy that into IntelliJ you can `Tools gt Kotlin gt Show Kotlin Bytecode` and then click the `Decompile` button at the top of the bytecode and see what Kotlin generated

harry.singh · Answer

I see Makes sense now +1

Rob Elliot · Answer

As you can see it generates a `public static void main` that calls your one which is why yours being private doesn t matter

Klitos Kyriacou · Answer

Then why doesn t `private fun main args Array lt String gt ` work

Klitos Kyriacou · Answer

Where does it say in Kotlin documentation that an executable entry point must be `fun main args Array lt String gt ` `fun main ` or `private fun main ` but not `private fun main args Array lt String gt `

Rob Elliot · Answer

I don t know about the documentation Using the decompiler if you provide `args Array lt String gt ` as an argument then it doesn t generate a synthetic main method at all so it can t make it public so that s why it doesn t work

Rob Elliot · Answer

```private fun main args Array lt String gt println hi ``` becomes ```public final class MainKt private static final void main String args String var1 = hi System out println var1 ```

Klitos Kyriacou · Answer

Thanks that makes sense Funnily enough IntelliJ IDEA still thinks it s executable and if you try to run it you get a JVM error

Joffrey · Answer

Not sure if generating a public synthetic for a private `main` should be considered a feature or a bug to be honest thinking face

harry.singh · Answer

I think the reason it doesn t generate the synthetic method in this case is because of the method signature conflict it would result into

Joffrey · Answer

Yes but it still doesn t explain why Kotlin finds it acceptable to generate a public synthetic for a `private fun main ` without arguments

Rob Elliot · Answer

I d guess a bug

Joffrey · Answer

Actually it does seem to be reported as a bug already <https youtrack jetbrains com issue KT 31582>

Joffrey · Answer

< Klitos Kyriacou> actually the fact that it s runnable from IDEA is also reported as a related but separate bug

Klitos Kyriacou · Answer

Thanks BTW it seems to do the right thing in Kotlin Native