go-delve/delve · error

not valid

Error message

not valid

What it means

On AMD64 Linux, the ABI has no dedicated link register (return addresses live on the stack), so AMD64Registers.LR() unconditionally panics. The proc.Registers interface includes LR for architectures like ARM64; calling it on AMD64 is always a logic error in the caller.

Source

Thrown at pkg/proc/linutil/regs_amd64_arch.go:134

func (r *AMD64Registers) BP() uint64 {
	return r.Regs.Rbp
}

// TLS returns the address of the thread local storage memory segment.
func (r *AMD64Registers) TLS() uint64 {
	return r.Regs.Fs_base
}

// GAddr returns the address of the G variable if it is known, 0 and false
// otherwise.
func (r *AMD64Registers) GAddr() (uint64, bool) {
	return 0, false
}

// LR returns the link register.
func (r *AMD64Registers) LR() uint64 {
	panic("not valid")
}

// Copy returns a copy of these registers that is guaranteed not to change.
func (r *AMD64Registers) Copy() (proc.Registers, error) {
	if r.loadFpRegs != nil {
		err := r.loadFpRegs(r)
		r.loadFpRegs = nil
		if err != nil {
			return nil, err
		}
	}
	var rr AMD64Registers
	rr.Regs = &AMD64PtraceRegs{}
	rr.Fpregset = &amd64util.AMD64Xstate{}
	*(rr.Regs) = *(r.Regs)
	if r.Fpregset != nil {
		*(rr.Fpregset) = *(r.Fpregset)
	}

View on GitHub (pinned to a23773e6c3)

Solutions

1. Only call LR() when the target architecture has a link register (arm64, etc.)
2. Use PC() and stack-pointer/frame APIs for unwinding on AMD64
3. Gate architecture-specific code with runtime.GOARCH or build tags

Example fix

// before
lr := regs.LR()
// after
var lr uint64
if goarch.IsArm64 > 0 { // or runtime.GOARCH == "arm64"
    lr = regs.LR()
}

if runtime.GOARCH == "amd64" { /* no LR: do not call */ }

func hasLinkRegister() bool {
    switch runtime.GOARCH {
    case "arm64", "riscv64", "loong64", "ppc64le":
        return true
    }
    return false
}

defer func() {
    if r := recover(); r != nil { err = fmt.Errorf("LR unavailable: %v", r) }
}()

When it happens

Trigger: Calling registers.LR() on an AMD64Registers value, e.g. frame-unwinding or stack-tracing code that assumes a RISC-style link register without checking GOARCH.

Common situations: Writing architecture-generic code that reads LR unconditionally; porting tools built on pkg/proc from ARM64 to AMD64; plugins/scripts built on delve internals.

Related errors

• not valid
• wrong number of bytes for register %s (%d)
• could not restore RFLAGS register: %v
• wrong number of bytes for register %s (%d)
• can not set %s

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/fd125f91437aeb5e. Report an issue: GitHub.