gdb/README.async

This branch is an attempt to get GDB to work asynchronously (whatever that
might mean).  I have started this by copying some changes from Apple's version
(CVS as of Sept 5 2005 and covered by GPL) to get some of the funtionality
that I'm looking for (and because I couldn't do it on my own!).  It uses
pthreads which Daniel Jacobowitz dislikes and thinks that it should be done in
one process.  Where I don't really understand the code changes, I have put
"Make asynchronous." and somtimes "(copied verbatim)" in the ChangeLog.

The initial changes are directed at the output of the asynchronous commands
such as run, continue, next, finish etc.  These are implemented through
mi_execute_async_cli_command and for asynchronus operation require
mi_exec_async_cli_cmd_continuation to be called through fetch_inferior event.

Currently -exec-next and next generate different output because the
asynchronous output is faked:

(gdb)
-exec-next
^running
(gdb)
*stopped,reason="end-stepping-range",thread-id="0",frame={addr="0x0804857f",func="main",args=[],file="myprog.c",fullname="/home/nickrob/myprog.c",line="69"}
(gdb)
n
&"n\n"
~"70\t  int n1 = 7, n2 = 8, n3 = 9;\n"
^done
(gdb)

With these changes the output is the same:

-exec-next
^running
(gdb)
*stopped,reason="end-stepping-range",thread-id="0",frame={addr="0x0804857f",func="main",args=[],file="myprog.c",fullname="/home/nickrob/myprog.c",line="69"}
(gdb)
n
&"n\n"
^running
^done
(gdb)
*stopped,reason="end-stepping-range",thread-id="0",frame={addr="0x080485bb",func="main",args=[],file="myprog.c",fullname="/home/nickrob/myprog.c",line="70"}
(gdb)

(actually it generates an extra &"n\n" and ^done but with 
"-interpreter-exec console" it's identical.

To enter a GDB command while the target is running GDB needs a separate
terminal to the inferior.  Currently only a few CLI commands can be entered
e.g pwd see top.c.  Most CLI commands report:

  Cannot execute this command while the target is running.

and all MI commands apart from -exec-interrupt (see mi-main.c) report:

  Cannot execute command interpreter-exec while target running

but this can easily be changed.

To help integration with HEAD I've re-instated the --async option so that
--noasync (the default) *should* run as on the trunk.

Bugs/Problems are in PROBLEMS.async

Further tasks in TODO.async

To run testsuite with asynchronous event loop put the line:

  set GDBFLAGS "--async"

at the bottom of site.exp.


Nick Roberts
nickrob@snap.net.nz