{"record":{"id":"e82e248418a40c82","repo":"golang/go","slug":"error-opening-profile-w-e82e24","errorCode":null,"errorMessage":"error opening profile: %w","messagePattern":"error opening profile: %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"src/cmd/preprofile/main.go","lineNumber":39,"sourceCode":"\t\"log\"\n\t\"os\"\n)\n\nfunc usage() {\n\tfmt.Fprintf(os.Stderr, \"usage: go tool preprofile [-V] [-o output] -i input\\n\\n\")\n\tflag.PrintDefaults()\n\tos.Exit(2)\n}\n\nvar (\n\toutput = flag.String(\"o\", \"\", \"output file path\")\n\tinput  = flag.String(\"i\", \"\", \"input pprof file path\")\n)\n\nfunc preprocess(profileFile string, outputFile string) error {\n\tf, err := os.Open(profileFile)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"error opening profile: %w\", err)\n\t}\n\tdefer f.Close()\n\n\tr := bufio.NewReader(f)\n\td, err := pgo.FromPProf(r)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"error parsing profile: %w\", err)\n\t}\n\n\tvar out *os.File\n\tif outputFile == \"\" {\n\t\tout = os.Stdout\n\t} else {\n\t\tout, err = os.Create(outputFile)\n\t\tif err != nil {\n\t\t\treturn fmt.Errorf(\"error creating output file: %w\", err)\n\t\t}\n\t\tdefer out.Close()","sourceCodeStart":21,"sourceCodeEnd":57,"githubUrl":"https://github.com/golang/go/blob/b6b368adc57c96c3151d224d172029f233ead2c3/src/cmd/preprofile/main.go#L21-L57","documentation":"The `preprofile` tool (Go's PGO profile preprocessor) failed to open the input pprof file specified by the `-i` flag. This is a standard OS-level file open error wrapped with context. The preprofile tool reads a pprof-format profile and converts it to an intermediate representation for use by the compiler during Profile-Guided Optimization (PGO).","triggerScenarios":"Fires at preprofile/main.go:38-39 when `os.Open(profileFile)` returns an error. The `profileFile` argument comes from the `-i` flag. This is typically invoked by the Go build system as `go tool preprofile -i input.pb.gz -o output` when PGO is enabled via `-pgo` flag in `go build`.","commonSituations":"The `-i` flag points to a file that doesn't exist or has a typo in the path. Insufficient file permissions to read the profile file. The profile path is relative and the working directory is wrong. The profile file was deleted or moved between generation and compilation. Using `-pgo` with an incorrect or stale profile path in go.mod or build configuration.","solutions":["Verify the profile file path is correct and the file exists: `ls -la <path>`.","Check file permissions: ensure the user running the build has read access to the profile file.","If using a relative path, ensure you're running the build from the correct directory, or switch to an absolute path.","Regenerate the profile file if it was deleted or corrupted: collect a new CPU profile and pass it to `-pgo`.","Check the `-pgo` path in your go.mod or build command for typos."],"exampleFix":"# Before: wrong or missing profile path\ngo build -pgo=nonexistent.pb.gz ./...\n\n# After: verify path exists and is accessible\nls -la default.pgo\ngo build -pgo=default.pgo ./...\n\n# Or regenerate profile\ngo test -cpuprofile=cpu.prof ./...\ngo build -pgo=cpu.prof ./...","handlingStrategy":"validation","validationCode":"// Validate profile file exists before passing to preprofile/-pgo\nprofilePath := \"default.pgo\"\nif _, err := os.Stat(profilePath); err != nil {\n    if os.IsNotExist(err) {\n        log.Fatalf(\"PGO profile not found: %s — generate it first\", profilePath)\n    }\n    log.Fatalf(\"Cannot access profile: %v\", err)\n}","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Always verify the PGO profile path exists before building with -pgo.","Use absolute paths for profile files in build scripts to avoid working-directory issues.","Keep profile files in a well-known location (e.g., the package directory as default.pgo).","Regenerate profiles after significant code changes to keep them valid."],"tags":["preprofile","pgo","profile-guided-optimization","file-io","build-tool"],"analyzedSha":"b6b368adc57c96c3151d224d172029f233ead2c3","analyzedAt":"2026-08-12T00:22:02.250Z","schemaVersion":2},"datasetVersion":"2026-08-12T08:17:17.861Z"}