required = append(required, fileFeatures(file, true)...)
	}
	exception := fileFeatures(filepath.Join(testenv.GOROOT(t), "api/except.txt"), false)

	if exitCode == 1 {
		t.Errorf("API database problems found")
	}
	if !compareAPI(bw, features, required, exception) {
		t.Errorf("API differences found")
	}
}

// export emits the exported package features.
func (w *Walker) export(pkg *apiPackage) {