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Wed, 22 Jan 2025 11:57:40 -0800 (PST) MIME-Version: 1.0 From: "Robert O'Callahan" Date: Thu, 23 Jan 2025 08:57:29 +1300 X-Gm-Features: AbW1kvbeXOlZrvJ6n86rWtjd8tBfW4l7-NSV2pRclr6oNpdAckKVOpMQ-IaNuo0 Message-ID: Subject: Incompatible implementat ion of 'x' packet in GDB vs LLDB To: gdb@sourceware.org Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.30 X-BeenThere: gdb@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gdb mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: robert@ocallahan.org Errors-To: gdb-bounces~public-inbox=simark.ca@sourceware.org Sender: "Gdb" 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. Thanks, Robert O'Callahan [1] https://sourceware.org/gdb/current/onlinedocs/gdb.html/Packets.html#Packets [2] https://github.com/bminor/binutils-gdb/blob/master/gdb/remote.c#L9739 [3] https://lldb.llvm.org/resources/lldbgdbremote.html#x-binary-memory-read [4] https://github.com/rr-debugger/rr/pull/3902 -- 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.