go runtime_error ai_generated true

panic: sync: negative WaitGroup counter

ID: go/negative-waitgroup-counter

Also available as: JSON · Markdown · 中文
80%Fix Rate
85%Confidence
0Evidence
2024-02-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.0 active — — —
1.21 active — — —

Root Cause

Calling Done() more times than Add() was called, decrementing counter below zero.

generic

中文

调用 Done() 的次数多于 Add() 的次数，导致计数器减到负数。

Workarounds

  1. 95% success Ensure Add() is called exactly once per goroutine that will call Done() 
    var wg sync.WaitGroup
for i := 0; i < n; i++ {
    wg.Add(1)
    go func() { defer wg.Done(); work() }()
}
wg.Wait()
  2. 90% success Use defer wg.Done() immediately after wg.Add() in the goroutine 
    go func() { defer wg.Done(); ... }()

Dead Ends

Common approaches that don't work:

  1. Increasing Add() count arbitrarily 85% fail

    If Done() is called extra times, the counter still goes negative.

  2. Ignoring the panic and continuing 100% fail

    Panic stops execution; ignoring it is not possible.