golang/go · error · entryNotFoundError

negative timestamp

Error message

negative timestamp

What it means

The timestamp field in the cache entry header parsed as a valid integer but is negative. The timestamp represents nanoseconds since Unix epoch and must be non-negative. The entry format space-pads the timestamp to 20 bytes; after stripping spaces and parsing, a negative value indicates corruption in the timestamp portion.

Source

Thrown at src/cmd/go/internal/cache/cache.go:255

	i := 0
	for i < len(esize) && esize[i] == ' ' {
		i++
	}
	size, err := strconv.ParseInt(string(esize[i:]), 10, 64)
	if err != nil {
		return missing(fmt.Errorf("parsing size: %v", err))
	} else if size < 0 {
		return missing(errors.New("negative size"))
	}
	i = 0
	for i < len(etime) && etime[i] == ' ' {
		i++
	}
	tm, err := strconv.ParseInt(string(etime[i:]), 10, 64)
	if err != nil {
		return missing(fmt.Errorf("parsing timestamp: %v", err))
	} else if tm < 0 {
		return missing(errors.New("negative timestamp"))
	}

	c.markUsed(c.fileName(id, "a"))

	return Entry{buf, size, time.Unix(0, tm)}, nil
}

// GetFile looks up the action ID in the cache and returns
// the name of the corresponding data file.
func GetFile(c Cache, id ActionID) (file string, entry Entry, err error) {
	entry, err = c.Get(id)
	if err != nil {
		return "", Entry{}, err
	}
	file = c.OutputFile(entry.OutputID)
	info, err := os.Stat(file)
	if err != nil {
		return "", Entry{}, &entryNotFoundError{Err: err}

View on GitHub (pinned to b6b368adc5)

Solutions

1. Run go clean -cache to purge corrupt entries
2. Run hardware diagnostics (memtest, disk SMART) if corruption recurs
3. Ensure consistent Go version across all builds sharing the cache
4. Check filesystem integrity

Example fix

// before: corrupt timestamp field in cache entry
// $ go build ./... # fails with 'cache entry not found: negative timestamp'

// after: clean cache
// $ go clean -cache && go build ./...

// No pre-check can predict timestamp field corruption.
// Same hardware reliability and cache hygiene practices apply.

func isNegativeTimestamp(err error) bool {
    return err != nil && strings.Contains(err.Error(), "negative timestamp")
}

// entry, err := cache.Get(id)
// if err != nil {
//     // Negative timestamp — corrupt timestamp field. Rebuild.
//     output = rebuild()
// }

When it happens

Trigger: DiskCache.get(id) parses the 20-byte space-padded timestamp field (etime) with strconv.ParseInt(s, 10, 64) after stripping leading spaces. The parse succeeds but tm < 0.

Common situations: Byte-level corruption in the timestamp field region of the entry file; storage errors affecting specific sectors; cache format incompatibility from mixing Go versions.

Related errors

• too long
• file is empty
• entry file incomplete
• invalid header
• mismatched ID

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/431a2186e4d6259d. Report an issue: GitHub.