//go:build (gc.conservative || gc.custom || gc.precise || gc.boehm) && moxie.wasm

package task

import "unsafe"

// gcData holds GC-relevant state for WASM tasks.
type gcData struct {
	stackTop uintptr
}

func (gcd *gcData) swap() {
	// On WASM, the stack is managed by the engine. Swap the stack top
	// pointer so the GC can scan the correct stack.
	gcd.stackTop, stackTop = stackTop, gcd.stackTop
}

// stackTop is the current stack top for GC scanning.
var stackTop uintptr

//go:export tinygo_scanCurrentStack
func scanCurrentStack() {
	// Mark from the current stack pointer to the stack top.
	scanstack(stackTop)
}

//go:linkname scanstack runtime.scanstack
func scanstack(uintptr)

//go:export tinygo_getStackTop
func getStackTop() uintptr {
	return stackTop
}

// SetStackTop is called by the runtime to set the top of the stack for GC.
//
//go:linkname SetStackTop runtime.setStackTop
func SetStackTop(top unsafe.Pointer) {
	stackTop = uintptr(top)
}