Merge pull request #428 from lukechampine/patch-1

Document undefined behavior in ForEach

bucket.go

@@ -346,7 +346,8 @@ func (b *Bucket) NextSequence() (uint64, error) {
 
 // ForEach executes a function for each key/value pair in a bucket.
 // If the provided function returns an error then the iteration is stopped and
-// the error is returned to the caller.
+// the error is returned to the caller. The provided function must not modify
+// the bucket; this will result in undefined behavior.
 func (b *Bucket) ForEach(fn func(k, v []byte) error) error {
 	if b.tx.db == nil {
 		return ErrTxClosed