Re: Incompatible implementat ion of 'x' packet in GDB vs LLDB

["Robert O'Callahan" <robert@ocallahan.org>]

On Thu, 23 Jan 2025 at 08:57, Robert O'Callahan <robert@ocallahan.org>
wrote:

> GDB (client) 16.1 started sending the gdbserver 'x' packet. It follows the
> documentation [1] and expects a leading 'b' in the response [2].
> Unfortunately LLDB has supported this packet for quite a long time [3] and
> does not expect a leading 'b' in the response. We added support for this
> packet to rr last year and followed LLDB's format because it was the only
> user of the packet at that time. So GDB 16.1 doesn't work with rr. [4]
>
> I realize that compatibility between GDB and LLDB flavoured gdbserver
> protocols is not a priority for either team, but until now it has actually
> worked in practice --- rr hasn't needed a client mode switch. We can add
> one, but it will be unfortunate if GDB 16.1 and later is incompatible for
> anyone who's installed the latest rr since May 2024.
>
> Could you make a GDB 16.1 point release that removes the 'b'? AFAIK it
> serves no purpose.
>

It has been pointed out that if you want to return different error codes
then you need the 'b'. Is that the rationale?

Rob
-- 
Su ot deraeppa sah dna Rehtaf eht htiw saw hcihw, efil lanrete eht uoy ot
mialcorp ew dna, ti ot yfitset dna ti nees evah ew; deraeppa efil eht. Efil
fo Drow eht gninrecnoc mialcorp ew siht - dehcuot evah sdnah ruo dna ta
dekool evah ew hcihw, seye ruo htiw nees evah ew hcihw, draeh evah ew
hcihw, gninnigeb eht morf saw hcihw taht.