RE: [PATCH 13/17] btrace: non-stop

["Metzger, Markus T" <markus dot t dot metzger at intel dot com>]

> -----Original Message-----
> From: Pedro Alves [mailto:palves@redhat.com]
> Sent: Wednesday, September 9, 2015 1:54 PM
> To: Metzger, Markus T
> Cc: gdb-patches@sourceware.org
> Subject: Re: [PATCH 13/17] btrace: non-stop
> 
> On 09/09/2015 11:35 AM, Markus Metzger wrote:
> 
> > +# make sure $line matches the full expected output per thread.
> > +# and let's hope that GDB never mixes the output from different threads.
> > +#
> > +# this is quite fragile, mostly because the prompt appears somewhere in
> > +# the middle of the output.
> > +proc gdb_cont_to { threads cmd line nthreads } {
> > +    global gdb_prompt
> > +    set full_cmd "thread apply $threads $cmd"
> > +    set prompt_seen 0
> > +
> > +    send_gdb "$full_cmd\n"
> > +
> > +    for {set i 0} {$i < $nthreads} {incr i} {
> > +        set test "$full_cmd: thread $i"
> > +
> > +        # check for the prompt.  it may be in front of one of the lines we
> > +        # try to match.
> > +        gdb_test_multiple "" "$test: check prompt" {
> > +            -notransfer -re "$gdb_prompt " {
> > +                set prompt_seen 1
> > +            }
> > +        }
> > +
> 
> Hmmm.  I'm not sure I'm missing some subtlety, but it seems to me
> that if you used -notransfer, then the prompt will still be in the buffer,
> and ...
> 
> > +        # check for the line.  and for a typical error.
> > +        gdb_test_multiple "" $test {
> > +            -re "Cannot execute this command \[^\\\r\\\n\]* is running\." {
> > +                fail $test
> > +            }
> > +            -re "$line\[^\\\r\\\n\]*\r\n" {
> > +                pass $test
> > +            }
> > +        }
> 
> ... thus this gdb_test_multiple can trip on it and issue a fail.

As far as I understand expect, the above gdb_test_multiple would
simply skip the $gdb_prompt at the beginning of the line.

That's why I'm trying to detect it with a separate gdb_test_multiple
above.  I use -notransfer so I can still analyse the line for the expected
output.


> Wouldn't this instead work?
> 
>         gdb_test_multiple "" $test {
>             -re "Cannot execute this command \[^\\\r\\\n\]* is running\." {
>                 fail $test
>             }
>             -re "$line\[^\\\r\\\n\]*\r\n" {
>                 pass $test
>             }
>             -re "$gdb_prompt " {
>                 set prompt_seen 1
>                 exp_continue
>             }
>        }

Wouldn't the 1st or 2nd pattern skip any $gdb_prompt before the pattern?
For the "Cannot execute..." pattern, I could add "^" but this will be difficult
for the $line pattern.

Does the 3rd pattern consume just the $gdb_prompt or the entire line?

This non-stop testing is quite difficult.  I also have not found too many
examples when I searched for "non-stop".

thanks,
Markus.

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