golang/go · error

error reading pkgconfig file %q: %v

Error message

error reading pkgconfig file %q: %v

What it means

Thrown by 'go tool cover' readPackageConfig when os.ReadFile fails on the -pkgcfg path. The wrapped error includes the path and the underlying OS error. The pkgcfg file is a JSON document (cmd/internal/cov/covcmd.CoverPkgConfig) produced by the go build toolchain describing the package to instrument.

Source

Thrown at src/cmd/cover/cover.go:219

		}
	} else if flag.NArg() == 0 {
		return nil
	}
	return fmt.Errorf("too many arguments")
}

func readOutFileList(path string) ([]string, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("error reading -outfilelist file %q: %v", path, err)
	}
	return strings.Split(strings.TrimSpace(string(data)), "\n"), nil
}

func readPackageConfig(path string) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return fmt.Errorf("error reading pkgconfig file %q: %v", path, err)
	}
	if err := json.Unmarshal(data, &pkgconfig); err != nil {
		return fmt.Errorf("error reading pkgconfig file %q: %v", path, err)
	}
	switch pkgconfig.Granularity {
	case "perblock":
		cgran = coverage.CtrGranularityPerBlock
	case "perfunc":
		cgran = coverage.CtrGranularityPerFunc
	default:
		return fmt.Errorf(`%s: pkgconfig requires perblock/perfunc value`, path)
	}
	return nil
}

// Block represents the information about a basic block to be recorded in the analysis.
// Note: Our definition of basic block is based on control structures; we don't break
// apart && and ||. We could but it doesn't seem important enough to bother.

View on GitHub (pinned to b6b368adc5)

Solutions

1. Confirm the -pkgcfg path exists and is readable
2. Use an absolute path
3. Normally let `go build -cover` generate and pass the pkgcfg file rather than hand-crafting it

Example fix

# before
go tool cover -mode=set -pkgcfg=p.cfg -outfilelist=o.txt input.go
# after (valid absolute path)
go tool cover -mode=set -pkgcfg=/abs/path/p.cfg -outfilelist=o.txt input.go

# Validate pkgcfg is readable before calling cover
if [ ! -r "$PKGCFG" ]; then echo "cannot read -pkgcfg $PKGCFG" >&2; exit 2; fi

When it happens

Trigger: `go tool cover -mode=set -pkgcfg=/missing/pkg.cfg ...` where the file cannot be read.

Common situations: The go command usually generates this file; hitting it manually with a wrong path. Relative path resolved from an unexpected CWD. Permissions. Race where the file was cleaned up before cover read it.

Related errors

• error reading -outfilelist file %q: %v
• can't read %q: %v
• please use '-outfilelist' flag instead of '-o'
• number of output files (%d) not equal to number of input fil
• '-outfilelist' flag applicable only when -pkgcfg used

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/aa16ae6af82f3f08. Report an issue: GitHub.