Re: Questions about GDB/MI

[Elena Zannoni <ezannoni at redhat dot com>]

Nick Roberts writes:
 > 
 > I'm trying to get my head round GDB/MI and have a few simple/dumb questions:
 > 
 > Simple example in info pages:
 > 
 > You say:
 > 
 > >    -> -stop
 > >    <- (gdb)
 > > 
 > > and later: 
 > >
 > >    <- *stop,reason="stop",address="0x123",source="a.c:123"
 > >    <- (gdb)
 > 
 > I get:
 > 
 > -> -stop
 > <- ^error,msg="Undefined MI command: stop"
 > <- (gdb) 
 > 

Hmmm, bogus docs. 'stop' as a command hasn't been implemented. There
is a comment in the .texinfo file about this. The command that does this is 
available only on async targets (remote), and is called exec-interrupt.

Could you file a bug report?

 > You say:
 > 
 > >     -> print 1+2
 > >     <- ~3\n
 > >     <- (gdb)
 > 
 > I get:
 > 
 > -> print 1+2
 > <- &"print 1+2\n"
 > <- ~"$1 = 3"
 > <- ~"\n"
 > <- ^done
 > <- (gdb) 
 > 

Are you lookng at html or ps?  In the .texinfo file the text is
correct, it is just not formatted properly:

@example
-> print 1+2
<- &"print 1+2\n"
<- ~"$1 = 3\n"
<- ^done
<- (@value{GDBP})
@end example

could you file another bug report?


 > Running a simple program, I get a sequence like:
 > 
 > -> -exec-next
 > <- ^running
 > <- (gdb) 
 > <- *stopped,reason="end-stepping-range",thread-id="0",frame={addr="0x08048578",func="main",args=[],file="myprog.c",line="18"}
 > <- (gdb) 
 > 
 > According to the GDB/MI Output Syntax shouldn't that be:
 > 
 > -> -exec-next
 > <- ^running
 > <- *stopped,reason="end-stepping-range",thread-id="0",frame={addr="0x08048578",func="main",args=[],file="myprog.c",line="18"}
 > <- (gdb) 
 > 
 > i.e isn't that one (gdb) too many?
 > 

I get the extra prompt too. Are you running on a native target?
Or on a remote target? On a remote target, the async capability of gdb
when running the inferior is real (if using 'target async'), while on
native, it is simulated. I wonder if there is a mismatch somewhere.
Anyway, if you are just running natively, it may be simply another doc
error.

Some of the documentation was written before we implemented the
commands, it evolved from a design doc into a user guide.

 > My simple program prints out:
 > 
 > a[0]=0
 > 
 > shouldn't that be:
 > 
 > @"a[0]=0"
 > 

Don't remember what the status of this is. Look through the bugs
database, for open MI bugs. But I see a testcase in the testsuite, and
code in the mi directory, so it should work.

 > Annotation uses ^Z^Z to flag things which I guess is not normal output. What
 > would happen if the program being debugged printed out strings like *stopped
 > or ^running? These only contain ASCII characters after all.
 > 

we added the number prefixes to the command, to help in cases like these
if you say:
222-exec-next
you would get
222^running
222*stopped

and you can match them.

 > And one question about the repository. I've checked out as Elena advised. I've
 > got the interp branch but every time I use `cvs update' in src, even without
 > the -d option it keeps on trying to give me other directories like binutils. I
 > have to go into gdb and do `cvs update' there where I just get gdbtk but I'm
 > worried that then I might be missing other files that I need..
 > 

yes, update -d at the top level brings in everything in the
repository, i.e.  ignores the fact you checked out just a single
module.  Use cvs update -dP (P prunes empty directories) in the gdb
directory. But if you followed the instructions from the web site, you
should have everything.

elena


 > Nick