Main.java

import java.lang.foreign.*;
import java.lang.invoke.*;

public class Main {
    public static void main(String[] args) throws Throwable {
        try (Arena arena = Arena.ofConfined()) {
            Linker linker = Linker.nativeLinker();
            SymbolLookup lookup = SymbolLookup.libraryLookup("tcl86t", arena).or(SymbolLookup.libraryLookup("tk86t", arena));

            MethodHandle createInterp = linker.downcallHandle(
                lookup.find("Tcl_CreateInterp").get(),
                FunctionDescriptor.of(ValueLayout.ADDRESS)
            );
            MethodHandle init = linker.downcallHandle(
                lookup.find("Tcl_Init").get(),
                FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS)
            );
            MethodHandle eval = linker.downcallHandle(
                lookup.find("Tcl_Eval").get(),
                FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS, ValueLayout.ADDRESS)
            );
            MethodHandle tk_init = linker.downcallHandle(
                lookup.find("Tk_Init").get(),
                FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS)
            );
            MethodHandle tk_mainloop = linker.downcallHandle(
                lookup.find("Tk_MainLoop").get(),
                FunctionDescriptor.ofVoid()
            );
            var interp = (MemorySegment)createInterp.invoke();

            eval.invoke(interp, arena.allocateFrom("set tcl_library {tcl8.6}"));
            eval.invoke(interp, arena.allocateFrom("set tk_library {tk8.6}"));

            int result0 = (int)init.invoke(interp);
            IO.println(result0);
            int result1 = (int)tk_init.invoke(interp);
            IO.println(result1);

            eval.invoke(interp, arena.allocateFrom("button .b -text \"click me\""));
            eval.invoke(interp, arena.allocateFrom("pack .b"));
            tk_mainloop.invoke();
        }
    }
}