Is stub support for the 's' packet optional or required?

[Kevin Buettner <kevinb at redhat dot com>]

I've been told off-list that it is not required for a stub to
implement support for the 's' packet.  I was also told that the
documenation is wrong in this regard.  Specifically, it says:

    A stub is required to support the `g', `G', `m', `M', `c', and `s'
    commands.  All other commands are optional.

See
    http://sources.redhat.com/gdb/current/onlinedocs/gdb_32.html#SEC632
and
    http://world.std.com/~qqi/download/protocol.txt

(I often find the latter document to be the more useful of the two.)

I'd like to get other opinions regarding this matter.  Also, if it
really is the case that stubs are NOT required to implement support
for the 's' packet, then will all such stubs return the empty response
which indicates that there is no support for that particular packet?

Kevin