golang/go · error

object is [%s] expected [%s]

Error message

object is [%s] expected [%s]

What it means

Returned when the object-file ABI header read from an export-data blob does not match the ABI header the running compiler expects (objabi.HeaderString()). It is a hard version gate: the object was produced by a compiler using a different object/ABI format and cannot be consumed.

Source

Thrown at src/cmd/compile/internal/noder/import.go:248

}

// readExportData returns the contents of GC-created unified export data.
func readExportData(f *os.File) (data string, err error) {
	r := bio.NewReader(f)

	sz, err := exportdata.FindPackageDefinition(r.Reader)
	if err != nil {
		return
	}
	end := r.Offset() + int64(sz)

	abihdr, _, err := exportdata.ReadObjectHeaders(r.Reader)
	if err != nil {
		return
	}

	if expect := objabi.HeaderString(); abihdr != expect {
		err = fmt.Errorf("object is [%s] expected [%s]", abihdr, expect)
		return
	}

	_, err = exportdata.ReadExportDataHeader(r.Reader)
	if err != nil {
		return
	}

	pos := r.Offset()

	// Map export data section (+ end-of-section marker) into memory
	// as a single large string. This reduces heap fragmentation and
	// allows returning individual substrings very efficiently.
	var mapped string
	mapped, err = base.MapFile(r.File(), pos, end-pos)
	if err != nil {
		return
	}

View on GitHub (pinned to b6b368adc5)

Solutions

1. go clean -cache to remove objects with mismatched ABI headers.
2. Ensure GOROOT and GOTOOLCHAIN point to the same Go version used to build the dependencies (go version, go env GOROOT GOTOOLCHAIN).
3. Rebuild all dependencies from source with the current toolchain (go build -a ./...).
4. Remove stale vendored .a files or third-party caches.

// Reject build inputs whose object ABI cannot match this compiler.
if !bytes.HasPrefix(objBytes, []byte(objabi.HeaderString())) {
    return errors.New("object ABI mismatch; rebuild with current toolchain")
}

When it happens

Trigger: exportdata.ReadObjectHeaders returns abihdr that differs from objabi.HeaderString(); the comparison at import.go:251 fails and the message reports both the found and expected headers.

Common situations: Mixing object files between Go major versions (e.g. 1.21 objects read by 1.22), a stale build cache from a previous toolchain, or a hand-built -importcfg referencing objects from another Go tree.

Related errors

• import %q: %v
• expected $$ marker, but found %q (recompile package)
• %s: %v
• marshal error %v
• internal error: collision during call site table merge, fn=%

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/59408f684d763d88. Report an issue: GitHub.