Re: How do I get regexp from expect at gdb_expect?

[Daniel Jacobowitz <drow@false.org>]

On Mon, Jan 31, 2005 at 10:06:52AM -0500, Bob Rossi wrote:
> On Fri, Jan 28, 2005 at 07:09:15PM -0800, Paul Hilfinger wrote:
> > 
> >  > Hi,
> >  > 
> >  > I'm using expect with GDB and I've come across a problem. For instance,
> >  > say I have,
> >  > 
> >  >     gdb_expect $tmt {
> >  >      -re "(Ending remote debugging.*$mi_gdb_prompt\[ \]*$)" {
> >  >         # at this point, how do I get the string that matched the above
> >  >         # regex?
> >  >         }
> >  >     }
> >  >     }
> > 
> > Here is some relevant documentation:
> > 
> >         Upon matching a pattern (or eof or  full_buffer),  any
> >         matching  and  previously unmatched output is saved in
> >         the variable expect_out(buffer) [as in $expect_out(buffer)].  
> >         Up to 9 regexp  sub-
> >         string    matches   are   saved   in   the   variables
> >         expect_out(1,string) through expect_out(9,string).  If
> >         the -indices flag is used before a pattern, the start-
> >         ing and ending indices (in a form suitable for lrange)
> >         of   the  10  strings  are  stored  in  the  variables
> >         expect_out(X,start) and expect_out(X,end) where X is a
> >         digit,  corresponds  to  the substring position in the
> >         buffer.  0 refers to strings which matched the  entire
> > 	pattern...
> 
> As an update, I've written the MI Output Command parser as a Tcl extension
> and I've put a call in mi-support.exp:mi_gdb_test to test the syntax of
> the MI Output Command.
> 
> I'm having a problem determining if GDB is broken, or if expect is
> giving me the wrong string back. I suspect it's the ladder.
> 
> Here's the place where I get the string from Expect, I do several lines
> of instrumentation. The data is below, everything after ### and before
> ### is what's given from Expect.
> 
>   -re "(\[\r\n\]*(($pattern)\[\r\n\]+$mi_gdb_prompt\[ \]*$))" {
>      set entire_out $expect_out(1,string)
>      set mi_out $expect_out(2,string)
>      set pattern_out $expect_out(3,string)
> 
>      set parse_result [gdbmi_parse $mi_out]
>      if [string match "syntax error" $parse_result] then {
>          fail "parsing MI output command"
>          puts "COMMAND($command)"
>          puts "ENTIRE_OUT###$entire_out###"
>          puts "PATTER_TO_END###$mi_out###"
>          puts "PATTER_OUT###$pattern_out###"
>          puts "BUFFER###$expect_out(buffer)###"
>      }
> 
>      if ![string match "" $message] then {
>      pass "$message"
>      }
>      set result 0
>  }

You've left out your pattern, and the context.  I recommend using
"exp_internal 1" to debug this sort of problem; that will show you what
expect is doing.

> The problem is, Expect is saying that '201-break-list' is part of the MI
> output command. This is incorrect and would mean that GDB is not
> behaving properly. However, the log file shows that GDB is *not*
> outputting the unwanted data as part of the MI Output Command,
> 
>    201-break-list^M
>    201^done,BreakpointTable={nr_rows="0",nr_cols="6",hdr=[{width="3",alignment="-1"
>    (gdb) ^M
>    FAIL: gdb.mi/mi-basics.exp: parsing MI output command

GDB echoes what you type.  Expect receives this and treats it as
output, because that's what it is.  You'll need to consume it
explicitly (but be careful - there are dragons here - what GDB outputs
may have extra non-printing characters for line wrapping on long
input).

-- 
Daniel Jacobowitz