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

[Darckfast]

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:

❯ 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

[aykevl]

-opt=0 doesn't work well, it usually disables too many optimizations. You'll probably want to use -opt=1.
(We should probably remove -opt=0 entirely)

[Darckfast]

thx, i will be using -opt=1

(We should probably remove -opt=0 entirely)

it might be a good idea, i got to opt=0 by following the https://tinygo.org/docs/guides/optimizing-binaries/ and testing what options helped with build times for wasm.

[0pcom]

Root cause: Go 1.25 added inBubble to internal/synctest (referenced from Bubble.Run). src/runtime/synctest.go stubs acquire and release but not inBubble, so any build where the reference survives dead-code elimination fails to link — -opt=0 with net/http being the reported case, but it is latent at any optimization level where the reference survives.

One-line fix (stub it next to the existing two; synctest is unsupported, so it runs f outside of any bubble, consistent with acquire returning nil): 0magnet/tinygo@1fce21f4a — branch synctest-inbubble-stub, ready as a PR: dev...0magnet:tinygo:synctest-inbubble-stub

Verified against the exact reproducer from this issue: fails to link without the stub, builds with it, and the default -opt path is unchanged.

(GitHub is currently refusing PR creation to this repository from my account — FORBIDDEN from createPullRequest while commenting and PRs to tinygo-org/net work fine — so posting the fix here for now; will open the PR when whatever restriction that is clears. If a maintainer wants to pull the commit in directly meanwhile, please do.)

[0pcom]

Status: re-verified the one-line stub against current dev today — the issue's exact reproducer fails to link without it and builds with it (-opt=0, js/wasm). PR creation to this repository is still refused for my account (createPullRequest FORBIDDEN; it briefly worked around Sep 1–2 when #5644–#5646 went through), so the branch remains at dev...0magnet:tinygo:synctest-inbubble-stub for anyone who wants to pull it in.

Also worth noting: #5649 implements synctest fully, including inBubble, and supersedes this stub whenever it lands — this branch is only the minimal stopgap for the link error.