Re: PATCH: Circular trace buffers

[Pedro Alves <pedro at codesourcery dot com>]

I see the patch went in, but how were the issues raised below addressed?
I don't understand why we'd want to have a "show circular-trace-buffer"
command that doesn't work correctly half the times, and hence can't
be trusted.  This means a frontend can not rely
on "-gdb-show circular-trace-buffer" to draw a toggle button, for
example (this is what I mean by calling it useless...).  I find
the disconnected-tracing example below quite alarming.

On Wednesday 17 March 2010 18:51:37, Pedro Alves wrote:
> On Wednesday 17 March 2010 18:04:52, Stan Shebs wrote:
> > > - this shows that "show circular-trace-buffer" is useless.
> > > - this requires users know that fact.
> > > - this doesn't sound user friendly.
> > >   
> > I'm just not seeing a problem myself - it seems obvious that circularity 
> > of trace buffer only matters for future tracepoint hits, and doesn't 
> > matter for completed trace runs, trace files, etc.  But I can rephrase 
> > the docs to make that clearer.
> 
> (Yes, please.  Okay, let's go with that then.)
> 
> Let me show you examples: hopefully it is easy to see with
> these how "show circular-trace-buffer" is broken as is.
> 
> 
> Please can we have the following inconsistencies resolved?:
> 
> Target supports circular:
> 
>  (gdb) tar rem :9999
>  (gdb) set circular-trace-buffer on
>  (gdb) show circular-trace-buffer
>  ... on.
> 
> Fine.
> 
> 
> Again, a target that supports circular, target wasn't
> tracing on initial connection (disconnect-tracing off):
> 
>  <not connected yet>
>  (gdb) set circular-trace-buffer on
>  (gdb) show circular-trace-buffer
>  ... on.
>  (gdb) tar rem :9999
>  (gdb) show circular-trace-buffer
>  ... on.
>  (gdb) set disconnected-tracing on
>  <set tracepoints>
>  (gdb) tstart
>  (gdb) detach
>  <end remote debug session>
>  (gdb) set circular-trace-buffer off
>  (gdb) tar rem :9999
>  (gdb) show circular-trace-buffer
>   ... off
> 
> Really "off"?  Ouch!  See?  QTstatus doesn't report the
> circularity-ness, but the circularity is logically part of
> the status of the current run.
> 
> Now against a target that _doesn't_ support QTBuffer (in circular mode):
> 
>  <not connected yet>
>  (gdb) set circular-trace-buffer on
>  (gdb) show circular-trace-buffer
>  ... on.
>  (gdb) tar rem :9999
>  <note, no complain, no warning>
>  (gdb) show circular-trace-buffer
>  Target's use of circular trace buffer is on.
> 
> Really?
> 
>  (gdb) set circular-trace-buffer off
>  Target does not support this command.
>  (gdb) set circular-trace-buffer on
>  Target does not support this command.
>  (gdb)
> 
> Ouch!
> 
> You can't easily try the latter case, because a new
> "set remote circular...-packet command is missing.

-- 
Pedro Alves