gdb/mi, new-ui. the console and determining when GDB is ready for the next command

Robert Rossi bob@brasko.net
Sat Nov 2 10:35:00 GMT 2019


Huh. Here is my setup.

$ gdb --version
GNU gdb (GDB) 8.3.1

On terminal one with gdb I have,
  $ gdb  -q -ex "new-ui mi /dev/pts/11" ./test_main
  Reading symbols from ./test_main...
  New UI allocated
  (gdb)
Terminal 2 shows
  $ tty
  /dev/pts/13
  $ sleep 1000
  =thread-group-added,id="i1"
  (gdb) <--- Good

So far everything is good. Now in terminal one I make a breakpoint.

Terminal 1 shows
  (gdb) b main
  Breakpoint 1 at 0x4006c0: file test.cpp, line 42.
  (gdb)
Terminal 2 shows
  (gdb)

=breakpoint-created,bkpt={number="1",type="breakpoint",...,original-location="main"}
<--- No GDB prompt

However it has no gdb prompt.
Now, if I run the program,

Terminal 1 shows,
  (gdb) r
  Starting program:.../test_main

  Breakpoint 1, main (argc=1, argv=0x7fffffffdea8) at test.cpp:42
  42      {
  (gdb)
Terminal 2 shows
  =thread-group-started,id="i1",pid="25913"
  =thread-created,id="1",group-id="i1"
  =library-loaded,id=...
  =library-loaded,id="/lib/x86_6....
  ~"\n"
  ~"Breakpoint 1, main (argc=1, argv=0x7fffffffdea8) at test.cpp:42\n"
  ~"42\t{\n"
  *stopped,reason="breakpoint-hit",...stopped-threads="all",core="0"
  <-- No GDB prompt

In this case also there is no gdb prompt.

Is this expected behavior or an oversight?

Thanks,
Bob Rossi

On Tue, Oct 29, 2019 at 9:21 AM Pedro Alves <palves@redhat.com> wrote:

> On 10/23/19 12:15 AM, Robert Rossi wrote:
> > Hi,
> >
> > The question I have is, how are people determining when GDB is ready for
> > the next
> > command when using the new-ui feature of GDB?
> > Are people parsing the CLI window for (gdb)?
> > Am I missing something obvious?
> >
> > CGDB has historically used annotations to communicate with gdb.
> > This provided pre-prompt and post-prompt annotations to determine when
> the
> > GDB prompt
> > was available and ready for the next command.
> >
> > A couple of years ago I decided to try to port CGDB from annotations to
> MI.
> > At the time I asked the GDB mailing list how to determine when GDB was
> > ready for the next
> > command, Pedro Alves wrote:
> >     GDB is ready for input when it prints the MI prompt.  There's one
> > prompt that is
> >     already printed after ^running that you should ignore. That's an
> > historical wart.
> > I got CGDB working but never completed the activity when I realized that
> > using -i=mi
> > caused GDB to no longer treat the terminal as an interactive terminal.
> > Meaning, GDB wouldn't do tab completion and/or ask the user if they were
> > ready to quit.
> >
> > Now I'm considering trying this again using the GDB new-ui feature.
> > In this mode the CLI remains in the starting terminal and the MI is moved
> > to the new-ui tty.
> > I noticed that in the new-ui window, the MI end token (gdb)\n isn't put
> > out. Is this intentional?
> > In this mode, what's the proper way to determine if GDB is ready for
> > another command?
>
> I'm not sure what you mean -- I see the end token being put out?
>
> Thanks,
> Pedro Alves
>
>



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