[binutils-gdb] gdb: Document vMustReplyEmpty remote packet

[Andrew Burgess <aburgess at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=176efed15cabb932a7e9fb2c5e6ef0753e8351a0

commit 176efed15cabb932a7e9fb2c5e6ef0753e8351a0
Author: Andrew Burgess <andrew.burgess@embecosm.com>
Date:   Mon May 15 10:11:57 2017 +0100

    gdb: Document vMustReplyEmpty remote packet
    
    Add mention of the vMustReplyEmpty to the remote serial protocol
    documentation.  It is important that this packet be treated in the same
    fashion as any other unknown 'v' packet, and I have tried to reflect
    this in the description of the packet, it is not simply the case that we
    _must_ return the empty string for this packet.
    
    As the intention is that we should treat this packet as unknown then an
    argument could be made that we should not document it, however, for
    someone implementing a gdbserver from scratch, seeing an undocumented
    packet arrive from gdb is confusing, and will probably cause them to
    have to read the code in order to check how this packet should be
    handled, which is not ideal.
    
    gdb/doc/ChangeLog:
    
    	* gdb.texinfo (Packets): Document vMustReplyEmpty packet.

Diff:
---
 gdb/doc/ChangeLog   |  4 ++++
 gdb/doc/gdb.texinfo | 13 +++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 8afb2e5..000f3c8 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,7 @@
+2017-05-22  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* gdb.texinfo (Packets): Document vMustReplyEmpty packet.
+
 2017-05-01  Tim Wiederhake  <tim.wiederhake@intel.com>
 
 	* python.texi (Recording in Python): Factor out the documentation of
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index f2e6156..9fb70f6 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -35827,6 +35827,19 @@ for an error
 for success
 @end table
 
+@item vMustReplyEmpty
+@cindex @samp{vMustReplyEmpty} packet
+The correct reply to an unknown @samp{v} packet is to return the empty
+string, however, some older versions of @command{gdbserver} would
+incorrectly return @samp{OK} for unknown @samp{v} packets.
+
+The @samp{vMustReplyEmpty} is used as a feature test to check how
+@command{gdbserver} handles unknown packets, it is important that this
+packet be handled in the same way as other unknown @samp{v} packets.
+If this packet is handled differently to other unknown @samp{v}
+packets then it is possile that @value{GDBN} may run into problems in
+other areas, specifically around use of @samp{vFile:setfs:}.
+
 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
 @cindex @samp{vRun} packet
 Run the program @var{filename}, passing it each @var{argument} on its