From 1fce21f40c32931009977cfd78dfe6bd7a26c6dc Mon Sep 17 00:00:00 2001
From: Moses Narrow <36607567+0pcom@users.noreply.github.com>
Date: Fri, 4 Sep 2026 18:59:10 -0500
Subject: [PATCH] runtime: stub internal/synctest.inBubble

Go 1.25 added inBubble to internal/synctest, referenced from
Bubble.Run. runtime/synctest.go stubs acquire and release but not
inBubble, so any build where the reference survives dead-code
elimination (notably -opt=0 with net/http) fails to link:

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

Add the missing stub. Synctest is unsupported, so it runs f outside
of any bubble, consistent with acquire returning nil.

Fixes #5495
---
 src/runtime/synctest.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/runtime/synctest.go b/src/runtime/synctest.go
index fa11c991fc..5e28869950 100644
--- a/src/runtime/synctest.go
+++ b/src/runtime/synctest.go
@@ -13,3 +13,9 @@ func synctest_acquire() any {
 func synctest_release(sg any) {
 	// Dummy: we don't support synctest.
 }
+
+//go:linkname synctest_inBubble internal/synctest.inBubble
+func synctest_inBubble(bubble any, f func()) {
+	// Dummy: we don't support synctest, so run f outside of any bubble.
+	f()
+}