warning: garbage in qC reply

[Emiliano Testa]

Hi Mathieu,
GDB is asking you to apply the next continue or step command to all threads
when it sends Hc-1:

from:
https://sourceware.org/gdb/onlinedocs/gdb/Packets.html#thread_002did-syntax

"Several packets and replies include a thread-id field to identify a
thread. Normally these are positive numbers with a target-specific
interpretation, formatted as big-endian hex strings. A thread-id can also
be a literal ‘-1’ to indicate all threads, or ‘0’ to pick any thread. "

So when receiving the Qc command your stub should reply with the currently
selected thread id, not -1.

Hope this helps

Emiliano



On Mon, 19 Nov 2018 at 16:34, Mathieu Tarral <mathieu.tarral@protonmail.com>
wrote:

> Hi,
>
> I'm writing a new GDB stub in Python, and while implementing
> each command that is sent to me by the GDB client during
> the attach phase, I'm facing an issue with the qC command:
>
> GDB is asking me to set the current thread-id to -1, with Hc-1
> and immediately after it query the current thread id, with qC
> I return -1 with QC-1, and I get a warning:
>
> Sending packet: $Hc-1#09...Ack
> Packet received: OK
> Sending packet: $qC#b4...Ack
> Packet received: QC-1
> warning: garbage in qC reply
>
> Is -1 an invalid thread-id syntax for qC ?
>
> Thanks !
> --
> Mathieu Tarral
>
> Sent with ProtonMail Secure Email.
>
>
>

-- 
Emiliano Testa
Undo software engineer

22 Station Road
Cambridge
CB1 2JD
United Kingdom