What causes "error opening profile: %w" in golang/go?

Verify the profile file exists at the specified path with os.Stat before building

error opening profile: %w

Error message

error opening profile: %w

What it means

The profile-guided optimization (PGO) subsystem opens a profile file via os.Open in pgoir.New(). This error wraps the underlying os.Open failure, which is typically a missing file, wrong path, or permission denied. The %w verb preserves the original error for unwrapping.

Source

Thrown at src/cmd/compile/internal/pgoir/irgraph.go:125

	Callee     *ir.Func
}

// Profile contains the processed PGO profile and weighted call graph used for
// PGO optimizations.
type Profile struct {
	// Profile is the base data from the raw profile, without IR attribution.
	*pgo.Profile

	// WeightedCG represents the IRGraph built from profile, which we will
	// update as part of inlining.
	WeightedCG *IRGraph
}

// New generates a profile-graph from the profile or pre-processed profile.
func New(profileFile string) (*Profile, error) {
	f, err := os.Open(profileFile)
	if err != nil {
		return nil, fmt.Errorf("error opening profile: %w", err)
	}
	defer f.Close()
	r := bufio.NewReader(f)

	isSerialized, err := pgo.IsSerialized(r)
	if err != nil {
		return nil, fmt.Errorf("error processing profile header: %w", err)
	}

	var base *pgo.Profile
	if isSerialized {
		base, err = pgo.FromSerialized(r)
		if err != nil {
			return nil, fmt.Errorf("error processing serialized PGO profile: %w", err)
		}
	} else {
		base, err = pgo.FromPProf(r)
		if err != nil {

View on GitHub (pinned to b6b368adc5)

Solutions

Verify the profile file exists at the specified path with os.Stat before building
Use a path relative to the module root, or use an absolute path
Regenerate the profile with: go test -cpuprofile=default.pgo ./...
Check file permissions: ensure the build process can read the profile file

Defensive patterns

Strategy: validation

Validate before calling

// Verify PGO profile exists and is readable before building
import (
    "os"
)

func validatePGOProfile(path string) error {
    info, err := os.Stat(path)
    if err != nil {
        return fmt.Errorf("PGO profile not accessible: %w", err)
    }
    if info.Size() == 0 {
        return fmt.Errorf("PGO profile is empty")
    }
    if !info.Mode().IsRegular() {
        return fmt.Errorf("PGO profile is not a regular file")
    }
    return nil
}

Prevention

Check that the PGO profile file exists before running go build -pgo
Use go test -cpuprofile to generate profiles rather than constructing them manually
Store profile files in a predictable location relative to the module root
Add the profile file to version control or a reliable artifact store in CI

When it happens

Trigger: Passing -pgo=/path/to/profile or -pgoprofile=/path where the file does not exist, is unreadable due to permissions, or the path is incorrect. The path can be absolute or relative to the working directory.

Common situations: CI pipelines where the PGO profile is not checked in or is generated in a different directory. Profile generation step failing or not running before the build step. Wrong working directory when the profile path is relative.

Related errors

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/7ed75e104a26ada7. Report an issue: GitHub.