go-delve/delve · error

unsupported pointer size %d

Error message

unsupported pointer size %d

What it means

writePointer panics with this error when the target architecture's pointer size is neither 4 nor 8 bytes. Delve only supports encoding pointers into the inferior's memory for 32-bit and 64-bit targets, so any other ptrbuf length indicates an unsupported or corrupted binary info arch setup. Because it panics rather than returns, it aborts the call-injection machinery mid-injection.

Source

Thrown at pkg/proc/fncall.go:471

	return "panic calling a function"
}

func fncallLog(fmtstr string, args ...any) {
	logflags.FnCallLogger().Infof(fmtstr, args...)
}

// writePointer writes val as an architecture pointer at addr in mem.
func writePointer(bi *BinaryInfo, mem MemoryReadWriter, addr, val uint64) error {
	ptrbuf := make([]byte, bi.Arch.PtrSize())

	// TODO: use target architecture endianness instead of LittleEndian
	switch len(ptrbuf) {
	case 4:
		binary.LittleEndian.PutUint32(ptrbuf, uint32(val))
	case 8:
		binary.LittleEndian.PutUint64(ptrbuf, val)
	default:
		panic(fmt.Errorf("unsupported pointer size %d", len(ptrbuf)))
	}
	_, err := mem.WriteMemory(addr, ptrbuf)
	return err
}

// callOP simulates a call instruction on the given thread:
// * pushes the current value of PC on the stack (adjusting SP)
// * changes the value of PC to callAddr
// Note: regs are NOT updated!
func callOP(bi *BinaryInfo, thread Thread, regs Registers, callAddr uint64) error {
	switch bi.Arch.Name {
	case "amd64":
		sp := regs.SP()
		// push PC on the stack
		sp -= uint64(bi.Arch.PtrSize())
		if err := setSP(thread, sp); err != nil {
			return err
		}

View on GitHub (pinned to a23773e6c3)

Solutions

1. Verify you are running on a supported architecture (386/amd64/arm64/etc. with ptr size 4 or 8)
2. Rebuild/reload the target so BinaryInfo.Arch is detected correctly
3. File a bug with the architecture details if ptr size is legitimately 4 or 8

Example fix

// before
panic(fmt.Errorf("unsupported pointer size %d", len(ptrbuf)))
// after
if len(ptrbuf) != 4 && len(ptrbuf) != 8 { return fmt.Errorf("unsupported pointer size %d", len(ptrbuf)) }

if bi.Arch.PtrSize() != 4 && bi.Arch.PtrSize() != 8 {
    return fmt.Errorf("call injection unsupported on ptr size %d", bi.Arch.PtrSize())
}

When it happens

Trigger: Calling a function (evalCallInjectionStart/callOP/writeString path) on a target whose bi.Arch.PtrSize() returns a value other than 4 or 8, or when the scratch pointer buffer was allocated with an unexpected length.

Common situations: Debugging on an exotic/unsupported architecture or a corrupted BinaryInfo where pointer size detection failed; also possible with mixed 32/64-bit mismatch between debugger and inferior.

Related errors

• internal debugger error: eval program finished without error
• internal debugger error: could not undo injected call during
• expression %q is not a function
• could not find DIE for function %q
• cannot use %s as argument %s in function %s: stack object pa

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/59785249182b66d7. Report an issue: GitHub.