wasm-ld: error: lto.tmp: undefined symbol: internal/synctest.inBubble

Author: DarckfastCreated Jul 4, 2026Updated Sep 5, 2026

when build the code below for WASM using -opt=0 it returns error

TinyGo: 0.41.1 (with roundtrip fix) Go: 1.24

//go:build js && wasm

package main

import (
        "net/http"
)

func main() {
        mux := http.NewServeMux()
        http.ListenAndServe(":8080", mux)
}

Error:

bash

❯ GOOS=js GOARCH=wasm tinygo build -opt=0 -o app.wasm
wasm-ld: error: lto.tmp: undefined symbol: internal/synctest.inBubble

the others -opt work fine

Source: tinygo-org/tinygo

View original on GitHub View discussion on GitHub