enable target async by default; separate MI and target notions of async

enable target async by default; separate MI and target notions of async

This finally makes background execution commands possible by default.

However, in order to do that, there's one last thing we need to do --
we need to separate the MI and target notions of "async".  Unlike the
CLI, where the user explicitly requests foreground vs background
execution in the execution command itself (c vs c&), MI chose to treat
"set target-async" specially -- setting it changes the default
behavior of execution commands.

So, we can't simply "set target-async" default to on, as that would
affect MI frontends.  Instead we have to make the setting MI-specific,
and teach MI about sync commands on top of an async target.

Because the "target" word in "set target-async" ends up as a potential
source of confusion, the patch adds a "set mi-async" option, and makes
"set target-async" a deprecated alias.

Rather than make the targets always async, this patch introduces a new
"maint set target-async" option so that the GDB developer can control
whether the target is async.  This makes it simpler to debug issues
arising only in the synchronous mode; important because sync mode
seems unlikely to go away.

Unlike in previous revisions, "set target-async" does not affect this
new maint parameter.  The rationale for this is that then one can
easily run the test suite in the "maint set target-async off" mode and
have tests that enable mi-async fail just like they fail on
non-async-capable targets.  This emulation is exactly the point of the
maint option.

I had asked Tom in a previous iteration to split the actual change of
the target async default to a separate patch, but it turns out that
that is quite awkward in this version of the patch, because with MI
async and target async decoupled (unlike in previous versions), if we
don't flip the default at the same time, then just "set target-async
on" alone never actually manages to do anything.  It's best to not
have that transitory state in the tree.

Given "set target-async on" now only has effect for MI, the patch goes
through the testsuite removing it from non-MI tests.  MI tests are
adjusted to use the new and less confusing "mi-async" spelling.

2014-05-29  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tromey@redhat.com>

	* NEWS: Mention "maint set target-async", "set mi-async", and that
	background execution commands are now always available.
	* target.h (target_async_permitted): Update comment.
	* target.c (target_async_permitted, target_async_permitted_1):
	Default to 1.
	(set_target_async_command): Rename to ...
	(maint_set_target_async_command): ... this.
	(show_target_async_command): Rename to ...
	(maint_show_target_async_command): ... this.
	(_initialize_target): Adjust.
	* infcmd.c (prepare_execution_command): Make extern.
	* inferior.h (prepare_execution_command): Declare.
	* infrun.c (set_observer_mode): Leave target async alone.
	* mi/mi-interp.c (mi_interpreter_init): Install
	mi_on_sync_execution_done as sync_execution_done observer.
	(mi_on_sync_execution_done): New function.
	(mi_execute_command_input_handler): Don't print the prompt if we
	just started a synchronous command with an async target.
	(mi_on_resume): Check sync_execution before printing prompt.
	* mi/mi-main.h (mi_async_p): Declare.
	* mi/mi-main.c: Include gdbcmd.h.
	(mi_async_p): New function.
	(mi_async, mi_async_1): New globals.
	(set_mi_async_command, show_mi_async_command, mi_async): New
	functions.
	(exec_continue): Call prepare_execution_command.
	(run_one_inferior, mi_cmd_exec_run, mi_cmd_list_target_features)
	(mi_execute_async_cli_command): Use mi_async_p.
	(_initialize_mi_main): Install "set mi-async".  Make
	"target-async" a deprecated alias.

2014-05-29  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tromey@redhat.com>

	* gdb.texinfo (Non-Stop Mode): Remove "set target-async 1"
	from example.
	(Asynchronous and non-stop modes): Document '-gdb-set mi-async'.
	Mention that target-async is now deprecated.
	(Maintenance Commands): Document maint set/show target-async.

2014-05-29  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tromey@redhat.com>

	* gdb.base/async-shell.exp: Don't enable target-async.
	* gdb.base/async.exp
	* gdb.base/corefile.exp (corefile_test_attach): Remove 'async'
	parameter.  Adjust.
	(top level): Don't test with "target-async".
	* gdb.base/dprintf-non-stop.exp: Don't enable target-async.
	* gdb.base/gdb-sigterm.exp: Don't test with "target-async".
	* gdb.base/inferior-died.exp: Don't enable target-async.
	* gdb.base/interrupt-noterm.exp: Likewise.
	* gdb.mi/mi-async.exp: Use "mi-async" instead of "target-async".
	* gdb.mi/mi-nonstop-exit.exp: Likewise.
	* gdb.mi/mi-nonstop.exp: Likewise.
	* gdb.mi/mi-ns-stale-regcache.exp: Likewise.
	* gdb.mi/mi-nsintrall.exp: Likewise.
	* gdb.mi/mi-nsmoribund.exp: Likewise.
	* gdb.mi/mi-nsthrexec.exp: Likewise.
	* gdb.mi/mi-watch-nonstop.exp: Likewise.
	* gdb.multi/watchpoint-multi.exp: Adjust comment.
	* gdb.python/py-evsignal.exp: Don't enable target-async.
	* gdb.python/py-evthreads.exp: Likewise.
	* gdb.python/py-prompt.exp: Likewise.
	* gdb.reverse/break-precsave.exp: Don't test with "target-async".
	* gdb.server/solib-list.exp: Don't enable target-async.
	* gdb.threads/thread-specific-bp.exp: Likewise.
	* lib/mi-support.exp: Adjust to use mi-async.