Re: [PATCH 3/3] gdb, gdbserver: introduce the 'x' RSP packet for binary memory read

[Tom Tromey <tom@tromey.com>]

>> Instead the idea is that if the packet is not explicitly forbidden
>> (either via a gdb command or by previous probe failure), just attempt to
>> use this packet for the first memory read.

> You mean, just as "x\0", without any arguments?  (Please also see the end
> of the email about this)

What I mean is refactor remote_read_bytes_1 to try the 'x' packet the
first time it is called (assuming the 'x' packet is not already banned).
If the remote replies that 'x' is unsupported, disable it and continue
to the 'm' packet.

> My first reaction would be that it depends on the given address.  If the
> address is accessible, it seems viable that a zero-length read is trivially
> a success, akin to defining an empty string.  If the address is not
> accessible, however, it would be an error.

I suspect not all remotes can make this determination.
So, if this is the semantics of a 0-length read, then maybe the packet
can't be used in some situations.

However I tend to think gdb should simply not do 0-length reads.

Tom