golang/go · error

%s: %v

Error message

%s: %v

What it means

Thrown by the Go compiler's gcimporter when opening an export-data file (object/archive) fails. A deferred closure prepends the file name to whatever I/O error os.Open returned, so the message reads as "<filename>: <underlying error>". It is purely an annotation wrapper; the real cause is whatever os.Open reported (missing file, permission denied, not an archive).

Source

Thrown at src/cmd/compile/internal/importer/gcimporter.go:68

				return types2.Unsafe, nil
			}
			return nil, err
		}

		// no need to re-import if the package was imported completely before
		if pkg = packages[id]; pkg != nil && pkg.Complete() {
			return
		}

		// open file
		f, err := os.Open(filename)
		if err != nil {
			return nil, err
		}
		defer func() {
			if err != nil {
				// add file name to error
				err = fmt.Errorf("%s: %v", filename, err)
			}
		}()
		rc = f
	}
	defer rc.Close()

	buf := bufio.NewReader(rc)
	data, err := exportdata.ReadUnified(buf)
	if err != nil {
		err = fmt.Errorf("import %q: %v", path, err)
		return
	}
	s := string(data)

	input := pkgbits.NewPkgDecoder(id, s)
	pkg = ReadPackage(nil, packages, input)

	return

View on GitHub (pinned to b6b368adc5)

Solutions

1. Run go clean -cache then rebuild to regenerate all object/export-data files.
2. Verify the path in the error message exists and is readable (ls -l <filename>).
3. Reinstall or rebuild the offending dependency with go install <pkg>@latest or go build ./... from a clean tree.
4. Check that GOROOT/GOTOOLCHAIN match the go version in use (go env GOROOT GOTOOLCHAIN).

// Before invoking the importer, ensure the resolved object file exists and is readable.
import "os"
if info, err := os.Stat(filename); err != nil || info.IsDir() {
    return fmt.Errorf("export data unavailable: %s", filename)
}

When it happens

Trigger: The compiler (or go/types importer) tries to read an object file's export data via gcimporter and os.Open(filename) returns a non-nil error; the deferred wrapper at gcimporter.go:68 then formats it. Triggers when the resolved filename does not exist, is unreadable, or points to a directory.

Common situations: Stale or partially-cleaned build cache (go clean -cache mid-build), corrupted GOROOT/GOPATH, switching Go toolchain versions without rebuilding dependencies, missing vendored object file, or a broken GOFLAGS/-importcfg pointing at a removed file.

Related errors

• import %q: %v
• %s: failed to read .go_export section: %v
• error opening target for caching: %w
• error adding target to cache: %w
• writing metafiles file: %v

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/02e9fc1e8fe3598e. Report an issue: GitHub.