Macro android_application 

macro_rules! android_application {
    ($content:path) => { ... };
    ($builder:expr, $content:path) => { ... };
}

Declares the Android entry point for an application whose root is a composable.

Android has no main: the Kotlin Activity owns the process and the frame loop, so the root is registered from JNI_OnLoad, which the generated shims reach through the symbol this defines.

compose_rust::android_application!(app);

The export exists only in a build for Android, for the reason ios_main! gives.