How does the compilation process convert suspend functions in Kotlin?

Suspend functions in Kotlin are transformed during compilation into functions with an additional parameter — a continuation object (Continuation).

This allows pausing the execution of a function and resuming it later, preserving the state.

For example, a suspend function:

suspend fun fetchData(): String {
    // ...
}

is compiled into a function with a Continuation parameter:

fun fetchData(continuation: Continuation<String>): Any {
    // implementation with state preservation
}

Inside such a function, a state machine mechanism is used to manage suspension and resumption points. This enables writing asynchronous code in a synchronous style.

Thus, suspend functions are syntactic sugar over callbacks and states, implemented through Continuation-passing style (CPS).