[Bug 1001614] New: eCos GDB stub "detach" reply incompatible with GDB 7.4.1

[Bug 1001614] New: eCos GDB stub "detach" reply incompatible with GDB 7.4.1

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           Summary: eCos GDB stub "detach" reply incompatible with GDB
                    7.4.1
           Product: eCos
           Version: CVS
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: normal
         Component: GDB stubs
        AssignedTo: unassigned@bugs.ecos.sourceware.org
        ReportedBy: john@dallaway.org.uk
                CC: ecos-bugs@ecos.sourceware.org
             Class: Advice Request


The generic eCos GDB stub code replies to a "D" detach packet with an empty
string. This causes GDB 7.4.1 to report "Remote doesn't know to detach".
According to GDB documentation, the GDB stub should reply "OK" to indicate
success - otherwise GDB will believe it is still attached to the target:

(gdb) det
Sending packet: $qTStatus#49...Ack
Packet received: 
Sending packet: $D#44...Ack
Packet received: 
Remote doesn't know how to detach
(gdb) 

Older GDB will interpret a reply of either "OK" or an empty string as an
indication of success (tested with GDB 5.3).

Patch to follow.

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[Bug 1001614] eCos GDB stub "detach" reply incompatible with GDB 7.4.1

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--- Comment #1 from John Dallaway <john@dallaway.org.uk> 2012-06-24 17:48:43 BST ---
Created an attachment (id=1803)
 --> (http://bugs.ecos.sourceware.org/attachment.cgi?id=1803)
gdb-stub-detach-120624.patch

The patch resolves the reported issue by replying "OK" (rather than an empty
string) to GDB detach requests ("D" packets).

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[Bug 1001614] eCos GDB stub "detach" reply incompatible with GDB 7.4.1

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Jonathan Larmour <jifl@ecoscentric.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |NEEDINFO
                 CC|                            |jifl@ecoscentric.com
         AssignedTo|unassigned@bugs.ecos.source |jifl@ecoscentric.com
                   |ware.org                    |

--- Comment #2 from Jonathan Larmour <jifl@ecoscentric.com> 2012-06-25 13:28:42 BST ---
The patch isn't right. GDB is correct - the remote side doesn't know how to
detach, hence the "null" packet rather than OK.

In all versions of GDB to date, GDB will stop talking to the target (closing
tcp socket if needed) anyway. I assume that is still the case in 7.4.1? e.g. if
you try and quit gdb, it won't complain it is still attached to the target. For
that reason at present we treat detach the same as 'kill', which this patch
wouldn't change. We treat it as 'kill' because it's arguably better to
potentially return to redboot (if applicable) than just get stuck forever in
the stub until a manual reset.

We could make a few changes to support detach properly with I think a bit of
extra code and a little global data, but is this an important enough feature to
add if no-one actually uses it the way it's intended? Presumably you don't
actually need the correct behaviour since this patch would continue to make it
identical to 'kill', as all this patch does is silence the message.

Jifl

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[Bug 1001614] New: eCos GDB stub "detach" reply incompatible with GDB 7.4.1

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           Summary: eCos GDB stub "detach" reply incompatible with GDB
                    7.4.1
           Product: eCos
           Version: CVS
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: normal
         Component: GDB stubs
        AssignedTo: unassigned@bugs.ecos.sourceware.org
        ReportedBy: john@dallaway.org.uk
                CC: ecos-bugs@ecos.sourceware.org
             Class: Advice Request


The generic eCos GDB stub code replies to a "D" detach packet with an empty
string. This causes GDB 7.4.1 to report "Remote doesn't know to detach".
According to GDB documentation, the GDB stub should reply "OK" to indicate
success - otherwise GDB will believe it is still attached to the target:

(gdb) det
Sending packet: $qTStatus#49...Ack
Packet received: 
Sending packet: $D#44...Ack
Packet received: 
Remote doesn't know how to detach
(gdb) 

Older GDB will interpret a reply of either "OK" or an empty string as an
indication of success (tested with GDB 5.3).

Patch to follow.

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