* xgate-dis.c (print_insn): Don't left shift signed value.
	(ripBits): Formatting, use 1u.

When building for mingw with -Wmissing-declarations, I get:

  CXX    gdbsupport/gdb_wait.o
/binutils-gdb/gdb/gdbsupport/gdb_wait.c:52:1: error: no previous declaration for 'int windows_status_to_termsig(long unsigned int)' [-Wer
ror=missing-declarations]
   52 | windows_status_to_termsig (unsigned long status)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~

Make gdb_wait.c include gdb_wait.h to fix it.

gdb/ChangeLog:

	* gdbsupport/gdb_wait.c: Include gdb_wait.h.

When building with -Wmissing-declarations, I get:

  CXX    linux-arm-tdesc.o
/binutils-gdb/gdb/gdbserver/linux-arm-tdesc.c:29:1: error: no previous declaration for 'const target_desc* arm_linux_read_description(arm_fp_type)' [-Werror=missing-declarations]
   29 | arm_linux_read_description (arm_fp_type fp_type)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~
/binutils-gdb/gdb/gdbserver/linux-arm-tdesc.c:49:1: error: no previous declaration for 'arm_fp_type arm_linux_get_tdesc_fp_type(const target_desc*)' [-Werror=missing-declarations]
   49 | arm_linux_get_tdesc_fp_type (const target_desc *tdesc)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~

Include linux-arm-tdesc.h in linux-arm-tdesc.c to fix it.  And because
linux-arm-tdesc.h uses the arm_fp_type, it should include arch/arm.h as
well.

gdb/gdbserver/ChangeLog:

	* linux-arm-tdesc.c: Include linux-arm-tdesc.h.
	* linux-arm-tdesc.h: Include arch/arm.h.

This function is only used in this file, so make it static.  It fixes
this error, when building with -Wmissing-declarations:

  CXX    linux-aarch64-low.o
/home/simark/src/binutils-gdb/gdb/gdbserver/linux-aarch64-low.c:2642:1: error: no previous declaration for 'void aarch64_write_goto_address(CORE_ADDR, CORE_ADDR, int)' [-Werror=missing-declarations]
 aarch64_write_goto_address (CORE_ADDR from, CORE_ADDR to, int size)
 ^~~~~~~~~~~~~~~~~~~~~~~~~~

gdb/gdbserver/ChangeLog:

	* linux-aarch64-low.c (aarch64_write_goto_address): Make static.

When building gdbserver for an aarch64 host with -Wmissing-declarations,
I see:

  CXX    linux-aarch32-tdesc.o
/home/simark/src/binutils-gdb/gdb/gdbserver/linux-aarch32-tdesc.c:28:1: error: no previous declaration for 'const target_desc* aarch32_linux_read_description()' [-Werror=missing-declarations]
 aarch32_linux_read_description ()
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/simark/src/binutils-gdb/gdb/gdbserver/linux-aarch32-tdesc.c:43:1: error: no previous declaration for 'bool is_aarch32_linux_description(const target_desc*)' [-Werror=missing-declarations]
 is_aarch32_linux_description (const target_desc *tdesc)
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

  CXX    linux-aarch64-tdesc.o
/home/simark/src/binutils-gdb/gdb/gdbserver/linux-aarch64-tdesc.c:32:1: error: no previous declaration for 'const target_desc* aarch64_linux_read_description(uint64_t, bool)' [-Werror=missing-declarations]
 aarch64_linux_read_description (uint64_t vq, bool pauth_p)
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix it by including linux-aarch32-tdesc.h in linux-aarch32-tdesc.c and
linux-aarch64-tdesc.h in linux-aarch64-tdesc.c.

gdb/gdbserver/ChangeLog:

	* linux-aarch32-tdesc.c: Include linux-aarch32-tdesc.h.
	* linux-aarch64-tdesc.c: Include linux-aarch64-tdesc.h.

The multi-target patch should have removed all traces of
discard_all_inferiors, but somehow one use stayed behind along with
the definition of the function.

discard_all_inferiors is bad now because it blindly exits inferiors of
all target connections.  It's best to remove it.

gdb/ChangeLog:
2020-01-12  Pedro Alves  <palves@redhat.com>

	* bsd-kvm.c (bsd_kvm_target::close): Call exit_inferior_silent
	directly for the current inferior instead of
	discard_all_inferiors.
	(discard_all_inferiors): Delete.

When adding support for styling the TUI borders, I neglected to have
this code check cli_styling.  As a result, "set style enabled off"
does not affect the borders.

This patch fixes this oversight.  While doing this, I found that
running gdb without an executable, enabling the TUI, and then trying
"set style enabled off" would fail with the mysterious "No registers".
The fix for this is to use deprecated_safe_get_selected_frame in
tui_source_window_base::refill.

gdb/ChangeLog
2020-01-11  Tom Tromey  <tom@tromey.com>

	* tui/tui-wingeneral.c (box_win): Check cli_styling.
	* tui/tui-winsource.c (tui_source_window_base::refill): Use
	deprecated_safe_get_selected_frame.

Change-Id: I36acda25dd9014d994d366b4a0e8faee9d95d0f8

GDB uses the 'current_top_target' when displaying the description of
an inferior.  This leads to same target being used for each inferior
and, in turn, yields incorrect output when the inferior has a target
that is supposed to give a specialized output.  For instance, the
remote target outputs "Remote target" instead of "process XYZ" as the
description if the multi-process feature is not supported or turned
off.

E.g.: Suppose we have a native and a remote target, and the native is
the current inferior.  The remote target does not support multi-process.
For "info inferiors", we would expect to see:

~~~
(gdb) i inferiors
  Num  Description       Connection       Executable
* 1    process 29060     1 (native)       /a/path
  2    Remote target     2 (remote ...)
~~~

but instead we get

~~~
(gdb) i inferiors
  Num  Description       Connection       Executable
* 1    process 29060     1 (native)       /a/path
  2    process 42000     2 (remote ...)
~~~

Similarly, if the current inferior is the remote one, we would expect
to see

~~~
(gdb) i inferiors
  Num  Description       Connection       Executable
  1    process 29060     1 (native)       /a/path
* 2    Remote target     2 (remote ...)
~~~

but we get

~~~
(gdb) i inferiors
  Num  Description       Connection       Executable
* 1    Remote target     1 (native)       /a/path
  2    Remote target     2 (remote ...)
~~~

With this patch, we switch to the inferior when outputting its
description, so that the current_top_target will be aligned to the
inferior we are displaying.

For testing, this patch expands the "info inferiors" test for the
multi-target feature.  The test was checking for the output of the
info commands after setup, only when the current inferior is the last
added inferior.

This patch does the following to the testcase:

1. The "info inferiors" and "info connections" test is extracted out
   from the "setup" procedure to a separate procedure.

2. The test is enriched to check the output after switching to each
   inferior, not just the last one.

3. The test is performed twice; one for when the multi-process feature
   is turned on, one for off.

gdb/ChangeLog:
2020-01-10  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* inferior.c (print_inferior): Switch inferior before printing it.

gdb/testsuite/ChangeLog:
2020-01-10  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* gdb.multi/multi-target.exp (setup): Factor out "info
	connections" and "info inferiors" tests to ...
	(test_info_inferiors): ... this new procedure.
	(top level): Run new "info-inferiors" tests.

With multi-target, each inferior now has its own target connection.
The problem in switch_to_program_space_and_thread is that in the
current state GDB switches to "no thread" and also sets the program
space but because the inferior is not switched, potentially an
incorrect target remains selected.

Here is a sample scenario that exploits this flow:

On terminal 1, start a gdbserver on a program named foo:

 $ gdbserver :1234 ./foo

On terminal 2, start gdb on a program named bar.  Suppose foo and bar
are compiled from foo.c and bar.c.  They are completely separate.  So,
bar.c:2 has no meaning for foo.

 $ gdb -q ./bar
 Reading symbols from ./bar...
 (gdb) add-inferior
 [New inferior 2]
 Added inferior 2
 (gdb) inferior 2
 [Switching to inferior 2 [<null>] (<noexec>)]
 (gdb) target remote :1234
 ...
 (gdb) set debug remote 2
 (gdb) break bar.c:2
 Sending packet: $Hgp0.0#ad...Packet received: OK
 Sending packet: $m5fa,12#f8...Packet received: E01
 Sending packet: $m5fa,1#c6...Packet received: E01
 Sending packet: $m5fb,3#c9...Packet received: E01
 Sending packet: $m5fe,1#ca...Packet received: E01
 Breakpoint 1 at 0x5fe: file bar.c, line 2.
 (gdb)

Here we have an unnecessary sending of the packets to the gdbserver.

With this fix in progspace-and-thread.c, we'll get this:

 (gdb) break bar.c:2
 Breakpoint 1 at 0x5fe: file bar.c, line 2.
 (gdb)

Now there is no sending of the packets to gdbserver.

The changes around clear_symtab_users calls are necessary because
otherwise we regress gdb.base/step-over-exit.exp, hitting the new
assertion in switch_to_program_space_and_thread.  The problem is, a
forked child terminates, and when GDB decides to auto-purge that
inferior, GDB tries to switch to the pspace of that no-longer-existing
inferior.

The root of the problem is within the program_space destructor:

program_space::~program_space ()
{
...
  set_current_program_space (this);        # (1)
...
  breakpoint_program_space_exit (this);    # (2)
...
  free_all_objfiles ();                    # (3)
...
}

We get here from delete_inferior -> delete_program_space.

So we're deleting an inferior, and the inferior to be
deleted is no longer in the inferior list.

At (2), we've deleted all the breakpoints and locations for the
program space being deleted.

The crash happens while doing a breakpoint re-set, called by
clear_symtab_users at the tail end of (3).  That is, while recreating
breakpoints for the current program space, which is the program space
we're tearing down.  During breakpoint re-set, we try to switch to the
new location's pspace (the current pspace set in (1), so the pspace
we're tearing down) with switch_to_program_space_and_thread, and that
hits the failed assertion.  It's the fact that we recreate breakpoints
in the program_space destructor that is the latent bug here.  Just
don't do that, and we don't end up in the crash situation.

My first approach to fix this added a symfile_add_flags parameter to
program_space::free_all_objfiles, and then passed that down to
clear_symtab_users.  The program_space dtor would then pass down
SYMFILE_DEFER_BP_RESET to free_all_objfiles.  I couldn't help feeling
that adding that parameter to free_all_objfiles looked a little
awkward, so I settled on something a little different -- hoist the
clear_symtab_users call to the callers.  There are only two callers.
I felt that that didn't look as odd, particularly since
remove_symbol_file_command also does:

  objf->unlink ();
  clear_symtab_users (0);

I.e., objfile deletion is already separate from calling
clear_symtab_users in some places.

gdb/ChangeLog:
2020-01-10  Aleksandar Paunovic  <aleksandar.paunovic@intel.com>
	    Pedro Alves  <palves@redhat.com>

	* progspace-and-thread.c (switch_to_program_space_and_thread):
	Assert there's an inferior for PSPACE.  Use
	switch_to_inferior_no_thread to switch the inferior too.
	* progspace.c (program_space::~program_space): Call
	clear_symtab_users here, with SYMFILE_DEFER_BP_RESET.
	(program_space::free_all_objfiles): Don't call clear_symtab_users
	here.
	* symfile.c (symbol_file_clear): Call clear_symtab_users here.

gdb/testsuite/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdb.server/bkpt-other-inferior.exp: New file.

This commit documents the new multi-target features in both NEWS and
user manual.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* NEWS: Mention multi-target debugging, "info connections", and
	"add-inferior -no-connection".

gdb/doc/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdb.texinfo (Starting): Say "current inferior not connected"
	instead of "GDB not connected".
	(Inferiors and Programs): Rename node to ...
	(Inferiors Connections and Programs): ... this.  Update all
	references.  Talk about multiple target connections.  Update "info
	inferiors" info to mention the connections column.  Describe "info
	connections".  Document "add-inferior -no-connection".
	* guile.texi, python.texi: Update cross references.

Currently, we can only support resuming multiple targets at the same
time if all targets are in non-stop mode (or user-visible all-stop
mode with target backend in non-stop mode).

This patch makes GDB error out if the user tries to resume more than
one target at the same time and one of the resumed targets isn't in
non-stop mode:

 (gdb) info inferiors
   Num  Description       Connection                Executable
   1    process 15303     1 (native)                a.out
 * 2    process 15286     2 (extended-remote :9999) a.out
 (gdb) set schedule-multiple on
 (gdb) c
 Continuing.
 Connection 2 (extended-remote :9999) does not support multi-target resumption.

This is here later in the series instead of in the main multi-target
patch because it depends the previous patch, which added
process_stratum_target::connection_string().

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* infrun.c: Include "target-connection.h".
	(check_multi_target_resumption): New.
	(proceed): Call it.
	* target-connection.c (make_target_connection_string): Make
	extern.
	* target-connection.h (make_target_connection_string): Declare.

This commit extends the CLI a bit for multi-target, in three ways.

#1 - New "info connections" command.

This is a new command that lists the open connections (process_stratum
targets).  For example, if you're debugging two remote connections, a
couple local/native processes, and a core dump, all at the same time,
you might see something like this:

 (gdb) info connections
   Num  What                     Description
   1    remote 192.168.0.1:9999  Remote serial target in gdb-specific protocol
   2    remote 192.168.0.2:9998  Remote serial target in gdb-specific protocol
 * 3    native                   Native process
   4    core                     Local core dump file

#2 - New "info inferiors" "Connection" column

You'll also see a new matching "Connection" column in "info
inferiors", showing you which connection an inferior is bound to:

 (gdb) info inferiors
   Num  Description       Connection                   Executable
   1    process 18526     1 (remote 192.168.0.1:9999)  target:/tmp/a.out
   2    process 18531     2 (remote 192.168.0.2:9998)  target:/tmp/a.out
   3    process 19115     3 (native)                   /tmp/prog1
   4    process 6286      4 (core)                     myprogram
 * 5    process 19122     3 (native)                   /bin/hello

#3 - Makes "add-inferior" show the inferior's target connection

"add-inferior" now shows you the connection you've just bound the
inferior to, which is the current process_stratum target:

 (gdb) add-inferior
 [New inferior 2]
 Added inferior 2 on connection 1 (extended-remote localhost:2346)

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* Makefile.in (COMMON_SFILES): Add target-connection.c.
	* inferior.c (uiout_field_connection): New function.
	(print_inferior): Add new "connection-id" column.
	(add_inferior_command): Show connection number/string of added
	inferior.
	* process-stratum-target.h
	(process_stratum_target::connection_string): New virtual method.
	(process_stratum_target::connection_number): New field.
	* remote.c (remote_target::connection_string): New override.
	* target-connection.c: New file.
	* target-connection.h: New file.
	* target.c (decref_target): Remove process_stratum targets from
	the connection list.
	(target_stack::push): Add process_stratum targets to the
	connection list.

gdb/testsuite/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdb.base/kill-detach-inferiors-cmd.exp: Adjust expected output
	of "add-inferior".
	* gdb.base/quit-live.exp: Likewise.
	* gdb.base/remote-exec-file.exp: Likewise.
	* gdb.guile/scm-progspace.exp: Likewise.
	* gdb.linespec/linespec.exp: Likewise.
	* gdb.mi/new-ui-mi-sync.exp: Likewise.
	* gdb.mi/user-selected-context-sync.exp: Likewise.
	* gdb.multi/multi-target.exp (setup): Add "info connection" and
	"info inferiors" tests.
	* gdb.multi/remove-inferiors.exp: Adjust expected output of
	"add-inferior".
	* gdb.multi/watchpoint-multi.exp: Likewise.
	* gdb.python/py-inferior.exp: Likewise.
	* gdb.server/extended-remote-restart.exp: Likewise.
	* gdb.threads/fork-plus-threads.exp: Adjust expected output of
	"info inferiors".
	* gdb.threads/forking-threads-plus-breakpoint.exp: Likewise.
	* gdb.trace/report.exp: Likewise.

This commit reverts:

 commit 5f5219fc
 Author:     Pedro Alves <palves@redhat.com>
 AuthorDate: Tue Apr 12 16:49:30 2016 +0100

     Remove unused struct serial::name field

The following patches will add uses for the field.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	Revert:
	2016-04-12  Pedro Alves  <palves@redhat.com>
	* serial.c (serial_open, serial_fdopen_ops, do_serial_close):
	Remove references to name.
	* serial.h (struct serial) <name>: Delete.

Since each inferior has its own target stack, the stratum condition
for the "error out if debugging something" check is always false.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdbarch-selftests.c (register_to_value_test): Remove "target
	already pushed" check.

This adds a testcase exercising multi-target features.  It spawns 6
inferiors, like this:

 inferior 1 -> native
 inferior 2 -> extended-remote 1
 inferior 3 -> core
 inferior 4 -> native
 inferior 5 -> extended-remote 2
 inferior 6 -> core

and then tests various details, including:

 - running to breakpoints

 - interrupting with Ctrl-C and "interrupt -a"

 - "next" bouncing between two breakpoints in two threads running in
   different targets.

 - since we have cores and live inferiors mixed in the same session,
   this makes sure that gdb doesn't try to remove a core dump's
   threads.

 - all-stop and non-stop modes.

This testcase caught a _lot_ of bugs in development.

gdb/testsuite/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdb.multi/multi-target.c: New file.
	* gdb.multi/multi-target.exp: New file.
	* lib/gdbserver-support.exp (gdb_target_cmd): Handle "Non-stop
	mode requested, but remote does not support non-stop".

This commit adds multi-target support to GDB.  What this means is that
with this commit, GDB can now be connected to different targets at the
same time.  E.g., you can debug a live native process and a core dump
at the same time, connect to multiple gdbservers, etc.

Actually, the word "target" is overloaded in gdb.  We already have a
target stack, with pushes several target_ops instances on top of one
another.  We also have "info target" already, which means something
completely different to what this patch does.

So from here on, I'll be using the "target connections" term, to mean
an open process_stratum target, pushed on a target stack.  This patch
makes gdb have multiple target stacks, and multiple process_stratum
targets open simultaneously.  The user-visible changes / commands will
also use this terminology, but of course it's all open to debate.

User-interface-wise, not that much changes.  The main difference is
that each inferior may have its own target connection.

A target connection (e.g., a target extended-remote connection) may
support debugging multiple processes, just as before.

Say you're debugging against gdbserver in extended-remote mode, and
you do "add-inferior" to prepare to spawn a new process, like:

 (gdb) target extended-remote :9999
 ...
 (gdb) start
 ...
 (gdb) add-inferior
 Added inferior 2
 (gdb) inferior 2
 [Switching to inferior 2 [<null>] (<noexec>)]
 (gdb) file a.out
 ...
 (gdb) start
 ...

At this point, you have two inferiors connected to the same gdbserver.

With this commit, GDB will maintain a target stack per inferior,
instead of a global target stack.

To preserve the behavior above, by default, "add-inferior" makes the
new inferior inherit a copy of the target stack of the current
inferior.  Same across a fork - the child inherits a copy of the
target stack of the parent.  While the target stacks are copied, the
targets themselves are not.  Instead, target_ops is made a
refcounted_object, which means that target_ops instances are
refcounted, which each inferior counting for a reference.

What if you want to create an inferior and connect it to some _other_
target?  For that, this commit introduces a new "add-inferior
-no-connection" option that makes the new inferior not share the
current inferior's target.  So you could do:

 (gdb) target extended-remote :9999
 Remote debugging using :9999
 ...
 (gdb) add-inferior -no-connection
 [New inferior 2]
 Added inferior 2
 (gdb) inferior 2
 [Switching to inferior 2 [<null>] (<noexec>)]
 (gdb) info inferiors
   Num  Description       Executable
   1    process 18401     target:/home/pedro/tmp/main
 * 2    <null>
 (gdb) tar extended-remote :10000
 Remote debugging using :10000
 ...
 (gdb) info inferiors
   Num  Description       Executable
   1    process 18401     target:/home/pedro/tmp/main
 * 2    process 18450     target:/home/pedro/tmp/main
 (gdb)

A following patch will extended "info inferiors" to include a column
indicating which connection an inferior is bound to, along with a
couple other UI tweaks.

Other than that, debugging is the same as before.  Users interact with
inferiors and threads as before.  The only difference is that
inferiors may be bound to processes running in different machines.

That's pretty much all there is to it in terms of noticeable UI
changes.

On to implementation.

Since we can be connected to different systems at the same time, a
ptid_t is no longer a unique identifier.  Instead a thread can be
identified by a pair of ptid_t and 'process_stratum_target *', the
later being the instance of the process_stratum target that owns the
process/thread.  Note that process_stratum_target inherits from
target_ops, and all process_stratum targets inherit from
process_stratum_target.  In earlier patches, many places in gdb were
converted to refer to threads by thread_info pointer instead of
ptid_t, but there are still places in gdb where we start with a
pid/tid and need to find the corresponding inferior or thread_info
objects.  So you'll see in the patch many places adding a
process_stratum_target parameter to functions that used to take only a
ptid_t.

Since each inferior has its own target stack now, we can always find
the process_stratum target for an inferior.  That is done via a
inf->process_target() convenience method.

Since each inferior has its own target stack, we need to handle the
"beneath" calls when servicing target calls.  The solution I settled
with is just to make sure to switch the current inferior to the
inferior you want before making a target call.  Not relying on global
context is just not feasible in current GDB.  Fortunately, there
aren't that many places that need to do that, because generally most
code that calls target methods already has the current context
pointing to the right inferior/thread.  Note, to emphasize -- there's
no method to "switch to this target stack".  Instead, you switch the
current inferior, and that implicitly switches the target stack.

In some spots, we need to iterate over all inferiors so that we reach
all target stacks.

Native targets are still singletons.  There's always only a single
instance of such targets.

Remote targets however, we'll have one instance per remote connection.

The exec target is still a singleton.  There's only one instance.  I
did not see the point of instanciating more than one exec_target
object.

After vfork, we need to make sure to push the exec target on the new
inferior.  See exec_on_vfork.

For type safety, functions that need a {target, ptid} pair to identify
a thread, take a process_stratum_target pointer for target parameter
instead of target_ops *.  Some shared code in gdb/nat/ also need to
gain a target pointer parameter.  This poses an issue, since gdbserver
doesn't have process_stratum_target, only target_ops.  To fix this,
this commit renames gdbserver's target_ops to process_stratum_target.
I think this makes sense.  There's no concept of target stack in
gdbserver, and gdbserver's target_ops really implements a
process_stratum-like target.

The thread and inferior iterator functions also gain
process_stratum_target parameters.  These are used to be able to
iterate over threads and inferiors of a given target.  Following usual
conventions, if the target pointer is null, then we iterate over
threads and inferiors of all targets.

I tried converting "add-inferior" to the gdb::option framework, as a
preparatory patch, but that stumbled on the fact that gdb::option does
not support file options yet, for "add-inferior -exec".  I have a WIP
patchset that adds that, but it's not a trivial patch, mainly due to
need to integrate readline's filename completion, so I deferred that
to some other time.

In infrun.c/infcmd.c, the main change is that we need to poll events
out of all targets.  See do_target_wait.  Right after collecting an
event, we switch the current inferior to an inferior bound to the
target that reported the event, so that target methods can be used
while handling the event.  This makes most of the code transparent to
multi-targets.  See fetch_inferior_event.

infrun.c:stop_all_threads is interesting -- in this function we need
to stop all threads of all targets.  What the function does is send an
asynchronous stop request to all threads, and then synchronously waits
for events, with target_wait, rinse repeat, until all it finds are
stopped threads.  Now that we have multiple targets, it's not
efficient to synchronously block in target_wait waiting for events out
of one target.  Instead, we implement a mini event loop, with
interruptible_select, select'ing on one file descriptor per target.
For this to work, we need to be able to ask the target for a waitable
file descriptor.  Such file descriptors already exist, they are the
descriptors registered in the main event loop with add_file_handler,
inside the target_async implementations.  This commit adds a new
target_async_wait_fd target method that just returns the file
descriptor in question.  See wait_one / stop_all_threads in infrun.c.

The 'threads_executing' global is made a per-target variable.  Since
it is only relevant to process_stratum_target targets, this is where
it is put, instead of in target_ops.

You'll notice that remote.c includes some FIXME notes.  These refer to
the fact that the global arrays that hold data for the remote packets
supported are still globals.  For example, if we connect to two
different servers/stubs, then each might support different remote
protocol features.  They might even be different architectures, like
e.g., one ARM baremetal stub, and a x86 gdbserver, to debug a
host/controller scenario as a single program.  That isn't going to
work correctly today, because of said globals.  I'm leaving fixing
that for another pass, since it does not appear to be trivial, and I'd
rather land the base work first.  It's already useful to be able to
debug multiple instances of the same server (e.g., a distributed
cluster, where you have full control over the servers installed), so I
think as is it's already reasonable incremental progress.

Current limitations:

 - You can only resume more that one target at the same time if all
   targets support asynchronous debugging, and support non-stop mode.
   It should be possible to support mixed all-stop + non-stop
   backends, but that is left for another time.  This means that
   currently in order to do multi-target with gdbserver you need to
   issue "maint set target-non-stop on".  I would like to make that
   mode be the default, but we're not there yet.  Note that I'm
   talking about how the target backend works, only.  User-visible
   all-stop mode works just fine.

 - As explained above, connecting to different remote servers at the
   same time is likely to produce bad results if they don't support the
   exact set of RSP features.

FreeBSD updates courtesy of John Baldwin.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>
	    John Baldwin  <jhb@FreeBSD.org>

	* aarch64-linux-nat.c
	(aarch64_linux_nat_target::thread_architecture): Adjust.
	* ada-tasks.c (print_ada_task_info): Adjust find_thread_ptid call.
	(task_command_1): Likewise.
	* aix-thread.c (sync_threadlists, aix_thread_target::resume)
	(aix_thread_target::wait, aix_thread_target::fetch_registers)
	(aix_thread_target::store_registers)
	(aix_thread_target::thread_alive): Adjust.
	* amd64-fbsd-tdep.c: Include "inferior.h".
	(amd64fbsd_get_thread_local_address): Pass down target.
	* amd64-linux-nat.c (ps_get_thread_area): Use ps_prochandle
	thread's gdbarch instead of target_gdbarch.
	* break-catch-sig.c (signal_catchpoint_print_it): Adjust call to
	get_last_target_status.
	* break-catch-syscall.c (print_it_catch_syscall): Likewise.
	* breakpoint.c (breakpoints_should_be_inserted_now): Consider all
	inferiors.
	(update_inserted_breakpoint_locations): Skip if inferiors with no
	execution.
	(update_global_location_list): When handling moribund locations,
	find representative inferior for location's pspace, and use thread
	count of its process_stratum target.
	* bsd-kvm.c (bsd_kvm_target_open): Pass target down.
	* bsd-uthread.c (bsd_uthread_target::wait): Use
	as_process_stratum_target and adjust thread_change_ptid and
	add_thread calls.
	(bsd_uthread_target::update_thread_list): Use
	as_process_stratum_target and adjust find_thread_ptid,
	thread_change_ptid and add_thread calls.
	* btrace.c (maint_btrace_packet_history_cmd): Adjust
	find_thread_ptid call.
	* corelow.c (add_to_thread_list): Adjust add_thread call.
	(core_target_open): Adjust add_thread_silent and thread_count
	calls.
	(core_target::pid_to_str): Adjust find_inferior_ptid call.
	* ctf.c (ctf_target_open): Adjust add_thread_silent call.
	* event-top.c (async_disconnect): Pop targets from all inferiors.
	* exec.c (add_target_sections): Push exec target on all inferiors
	sharing the program space.
	(remove_target_sections): Remove the exec target from all
	inferiors sharing the program space.
	(exec_on_vfork): New.
	* exec.h (exec_on_vfork): Declare.
	* fbsd-nat.c (fbsd_add_threads): Add fbsd_nat_target parameter.
	Pass it down.
	(fbsd_nat_target::update_thread_list): Adjust.
	(fbsd_nat_target::resume): Adjust.
	(fbsd_handle_debug_trap): Add fbsd_nat_target parameter.  Pass it
	down.
	(fbsd_nat_target::wait, fbsd_nat_target::post_attach): Adjust.
	* fbsd-tdep.c (fbsd_corefile_thread): Adjust
	get_thread_arch_regcache call.
	* fork-child.c (gdb_startup_inferior): Pass target down to
	startup_inferior and set_executing.
	* gdbthread.h (struct process_stratum_target): Forward declare.
	(add_thread, add_thread_silent, add_thread_with_info)
	(in_thread_list): Add process_stratum_target parameter.
	(find_thread_ptid(inferior*, ptid_t)): New overload.
	(find_thread_ptid, thread_change_ptid): Add process_stratum_target
	parameter.
	(all_threads()): Delete overload.
	(all_threads, all_non_exited_threads): Add process_stratum_target
	parameter.
	(all_threads_safe): Use brace initialization.
	(thread_count): Add process_stratum_target parameter.
	(set_resumed, set_running, set_stop_requested, set_executing)
	(threads_are_executing, finish_thread_state): Add
	process_stratum_target parameter.
	(switch_to_thread): Use is_current_thread.
	* i386-fbsd-tdep.c: Include "inferior.h".
	(i386fbsd_get_thread_local_address): Pass down target.
	* i386-linux-nat.c (i386_linux_nat_target::low_resume): Adjust.
	* inf-child.c (inf_child_target::maybe_unpush_target): Remove
	have_inferiors check.
	* inf-ptrace.c (inf_ptrace_target::create_inferior)
	(inf_ptrace_target::attach): Adjust.
	* infcall.c (run_inferior_call): Adjust.
	* infcmd.c (run_command_1): Pass target to
	scoped_finish_thread_state.
	(proceed_thread_callback): Skip inferiors with no execution.
	(continue_command): Rename 'all_threads' local to avoid hiding
	'all_threads' function.  Adjust get_last_target_status call.
	(prepare_one_step): Adjust set_running call.
	(signal_command): Use user_visible_resume_target.  Compare thread
	pointers instead of inferior_ptid.
	(info_program_command): Adjust to pass down target.
	(attach_command): Mark target's 'thread_executing' flag.
	(stop_current_target_threads_ns): New, factored out from ...
	(interrupt_target_1): ... this.  Switch inferior before making
	target calls.
	* inferior-iter.h
	(struct all_inferiors_iterator, struct all_inferiors_range)
	(struct all_inferiors_safe_range)
	(struct all_non_exited_inferiors_range): Filter on
	process_stratum_target too.  Remove explicit.
	* inferior.c (inferior::inferior): Push dummy target on target
	stack.
	(find_inferior_pid, find_inferior_ptid, number_of_live_inferiors):
	Add process_stratum_target parameter, and pass it down.
	(have_live_inferiors): Adjust.
	(switch_to_inferior_and_push_target): New.
	(add_inferior_command, clone_inferior_command): Handle
	"-no-connection" parameter.  Use
	switch_to_inferior_and_push_target.
	(_initialize_inferior): Mention "-no-connection" option in
	the help of "add-inferior" and "clone-inferior" commands.
	* inferior.h: Include "process-stratum-target.h".
	(interrupt_target_1): Use bool.
	(struct inferior) <push_target, unpush_target, target_is_pushed,
	find_target_beneath, top_target, process_target, target_at,
	m_stack>: New.
	(discard_all_inferiors): Delete.
	(find_inferior_pid, find_inferior_ptid, number_of_live_inferiors)
	(all_inferiors, all_non_exited_inferiors): Add
	process_stratum_target parameter.
	* infrun.c: Include "gdb_select.h" and <unordered_map>.
	(target_last_proc_target): New global.
	(follow_fork_inferior): Push target on new inferior.  Pass target
	to add_thread_silent.  Call exec_on_vfork.  Handle target's
	reference count.
	(follow_fork): Adjust get_last_target_status call.  Also consider
	target.
	(follow_exec): Push target on new inferior.
	(struct execution_control_state) <target>: New field.
	(user_visible_resume_target): New.
	(do_target_resume): Call target_async.
	(resume_1): Set target's threads_executing flag.  Consider resume
	target.
	(commit_resume_all_targets): New.
	(proceed): Also consider resume target.  Skip threads of inferiors
	with no execution.  Commit resumtion in all targets.
	(start_remote): Pass current inferior to wait_for_inferior.
	(infrun_thread_stop_requested): Consider target as well.  Pass
	thread_info pointer to clear_inline_frame_state instead of ptid.
	(infrun_thread_thread_exit): Consider target as well.
	(random_pending_event_thread): New inferior parameter.  Use it.
	(do_target_wait): Rename to ...
	(do_target_wait_1): ... this.  Add inferior parameter, and pass it
	down.
	(threads_are_resumed_pending_p, do_target_wait): New.
	(prepare_for_detach): Adjust calls.
	(wait_for_inferior): New inferior parameter.  Handle it.  Use
	do_target_wait_1 instead of do_target_wait.
	(fetch_inferior_event): Adjust.  Switch to representative
	inferior.  Pass target down.
	(set_last_target_status): Add process_stratum_target parameter.
	Save target in global.
	(get_last_target_status): Add process_stratum_target parameter and
	handle it.
	(nullify_last_target_wait_ptid): Clear 'target_last_proc_target'.
	(context_switch): Check inferior_ptid == null_ptid before calling
	inferior_thread().
	(get_inferior_stop_soon): Pass down target.
	(wait_one): Rename to ...
	(poll_one_curr_target): ... this.
	(struct wait_one_event): New.
	(wait_one): New.
	(stop_all_threads): Adjust.
	(handle_no_resumed, handle_inferior_event): Adjust to consider the
	event's target.
	(switch_back_to_stepped_thread): Also consider target.
	(print_stop_event): Update.
	(normal_stop): Update.  Also consider the resume target.
	* infrun.h (wait_for_inferior): Remove declaration.
	(user_visible_resume_target): New declaration.
	(get_last_target_status, set_last_target_status): New
	process_stratum_target parameter.
	* inline-frame.c (clear_inline_frame_state(ptid_t)): Add
	process_stratum_target parameter, and use it.
	(clear_inline_frame_state (thread_info*)): New.
	* inline-frame.c (clear_inline_frame_state(ptid_t)): Add
	process_stratum_target parameter.
	(clear_inline_frame_state (thread_info*)): Declare.
	* linux-fork.c (delete_checkpoint_command): Pass target down to
	find_thread_ptid.
	(checkpoint_command): Adjust.
	* linux-nat.c (linux_nat_target::follow_fork): Switch to thread
	instead of just tweaking inferior_ptid.
	(linux_nat_switch_fork): Pass target down to thread_change_ptid.
	(exit_lwp): Pass target down to find_thread_ptid.
	(attach_proc_task_lwp_callback): Pass target down to
	add_thread/set_running/set_executing.
	(linux_nat_target::attach): Pass target down to
	thread_change_ptid.
	(get_detach_signal): Pass target down to find_thread_ptid.
	Consider last target status's target.
	(linux_resume_one_lwp_throw, resume_lwp)
	(linux_handle_syscall_trap, linux_handle_extended_wait, wait_lwp)
	(stop_wait_callback, save_stop_reason, linux_nat_filter_event)
	(linux_nat_wait_1, resume_stopped_resumed_lwps): Pass target down.
	(linux_nat_target::async_wait_fd): New.
	(linux_nat_stop_lwp, linux_nat_target::thread_address_space): Pass
	target down.
	* linux-nat.h (linux_nat_target::async_wait_fd): Declare.
	* linux-tdep.c (get_thread_arch_regcache): Pass target down.
	* linux-thread-db.c (struct thread_db_info::process_target): New
	field.
	(add_thread_db_info): Save target.
	(get_thread_db_info): New process_stratum_target parameter.  Also
	match target.
	(delete_thread_db_info): New process_stratum_target parameter.
	Also match target.
	(thread_from_lwp): Adjust to pass down target.
	(thread_db_notice_clone): Pass down target.
	(check_thread_db_callback): Pass down target.
	(try_thread_db_load_1): Always push the thread_db target.
	(try_thread_db_load, record_thread): Pass target down.
	(thread_db_target::detach): Pass target down.  Always unpush the
	thread_db target.
	(thread_db_target::wait, thread_db_target::mourn_inferior): Pass
	target down.  Always unpush the thread_db target.
	(find_new_threads_callback, thread_db_find_new_threads_2)
	(thread_db_target::update_thread_list): Pass target down.
	(thread_db_target::pid_to_str): Pass current inferior down.
	(thread_db_target::get_thread_local_address): Pass target down.
	(thread_db_target::resume, maintenance_check_libthread_db): Pass
	target down.
	* nto-procfs.c (nto_procfs_target::update_thread_list): Adjust.
	* procfs.c (procfs_target::procfs_init_inferior): Declare.
	(proc_set_current_signal, do_attach, procfs_target::wait): Adjust.
	(procfs_init_inferior): Rename to ...
	(procfs_target::procfs_init_inferior): ... this and adjust.
	(procfs_target::create_inferior, procfs_notice_thread)
	(procfs_do_thread_registers): Adjust.
	* ppc-fbsd-tdep.c: Include "inferior.h".
	(ppcfbsd_get_thread_local_address): Pass down target.
	* proc-service.c (ps_xfer_memory): Switch current inferior and
	program space as well.
	(get_ps_regcache): Pass target down.
	* process-stratum-target.c
	(process_stratum_target::thread_address_space)
	(process_stratum_target::thread_architecture): Pass target down.
	* process-stratum-target.h
	(process_stratum_target::threads_executing): New field.
	(as_process_stratum_target): New.
	* ravenscar-thread.c
	(ravenscar_thread_target::update_inferior_ptid): Pass target down.
	(ravenscar_thread_target::wait, ravenscar_add_thread): Pass target
	down.
	* record-btrace.c (record_btrace_target::info_record): Adjust.
	(record_btrace_target::record_method)
	(record_btrace_target::record_is_replaying)
	(record_btrace_target::fetch_registers)
	(get_thread_current_frame_id, record_btrace_target::resume)
	(record_btrace_target::wait, record_btrace_target::stop): Pass
	target down.
	* record-full.c (record_full_wait_1): Switch to event thread.
	Pass target down.
	* regcache.c (regcache::regcache)
	(get_thread_arch_aspace_regcache, get_thread_arch_regcache): Add
	process_stratum_target parameter and handle it.
	(current_thread_target): New global.
	(get_thread_regcache): Add process_stratum_target parameter and
	handle it.  Switch inferior before calling target method.
	(get_thread_regcache): Pass target down.
	(get_thread_regcache_for_ptid): Pass target down.
	(registers_changed_ptid): Add process_stratum_target parameter and
	handle it.
	(registers_changed_thread, registers_changed): Pass target down.
	(test_get_thread_arch_aspace_regcache): New.
	(current_regcache_test): Define a couple local test_target_ops
	instances and use them for testing.
	(readwrite_regcache): Pass process_stratum_target parameter.
	(cooked_read_test, cooked_write_test): Pass mock_target down.
	* regcache.h (get_thread_regcache, get_thread_arch_regcache)
	(get_thread_arch_aspace_regcache): Add process_stratum_target
	parameter.
	(regcache::target): New method.
	(regcache::regcache, regcache::get_thread_arch_aspace_regcache)
	(regcache::registers_changed_ptid): Add process_stratum_target
	parameter.
	(regcache::m_target): New field.
	(registers_changed_ptid): Add process_stratum_target parameter.
	* remote.c (remote_state::supports_vCont_probed): New field.
	(remote_target::async_wait_fd): New method.
	(remote_unpush_and_throw): Add remote_target parameter.
	(get_current_remote_target): Adjust.
	(remote_target::remote_add_inferior): Push target.
	(remote_target::remote_add_thread)
	(remote_target::remote_notice_new_inferior)
	(get_remote_thread_info): Pass target down.
	(remote_target::update_thread_list): Skip threads of inferiors
	bound to other targets.  (remote_target::close): Don't discard
	inferiors.  (remote_target::add_current_inferior_and_thread)
	(remote_target::process_initial_stop_replies)
	(remote_target::start_remote)
	(remote_target::remote_serial_quit_handler): Pass down target.
	(remote_target::remote_unpush_target): New remote_target
	parameter.  Unpush the target from all inferiors.
	(remote_target::remote_unpush_and_throw): New remote_target
	parameter.  Pass it down.
	(remote_target::open_1): Check whether the current inferior has
	execution instead of checking whether any inferior is live.  Pass
	target down.
	(remote_target::remote_detach_1): Pass down target.  Use
	remote_unpush_target.
	(extended_remote_target::attach): Pass down target.
	(remote_target::remote_vcont_probe): Set supports_vCont_probed.
	(remote_target::append_resumption): Pass down target.
	(remote_target::append_pending_thread_resumptions)
	(remote_target::remote_resume_with_hc, remote_target::resume)
	(remote_target::commit_resume): Pass down target.
	(remote_target::remote_stop_ns): Check supports_vCont_probed.
	(remote_target::interrupt_query)
	(remote_target::remove_new_fork_children)
	(remote_target::check_pending_events_prevent_wildcard_vcont)
	(remote_target::remote_parse_stop_reply)
	(remote_target::process_stop_reply): Pass down target.
	(first_remote_resumed_thread): New remote_target parameter.  Pass
	it down.
	(remote_target::wait_as): Pass down target.
	(unpush_and_perror): New remote_target parameter.  Pass it down.
	(remote_target::readchar, remote_target::remote_serial_write)
	(remote_target::getpkt_or_notif_sane_1)
	(remote_target::kill_new_fork_children, remote_target::kill): Pass
	down target.
	(remote_target::mourn_inferior): Pass down target.  Use
	remote_unpush_target.
	(remote_target::core_of_thread)
	(remote_target::remote_btrace_maybe_reopen): Pass down target.
	(remote_target::pid_to_exec_file)
	(remote_target::thread_handle_to_thread_info): Pass down target.
	(remote_target::async_wait_fd): New.
	* riscv-fbsd-tdep.c: Include "inferior.h".
	(riscv_fbsd_get_thread_local_address): Pass down target.
	* sol2-tdep.c (sol2_core_pid_to_str): Pass down target.
	* sol-thread.c (sol_thread_target::wait, ps_lgetregs, ps_lsetregs)
	(ps_lgetfpregs, ps_lsetfpregs, sol_update_thread_list_callback):
	Adjust.
	* solib-spu.c (spu_skip_standalone_loader): Pass down target.
	* solib-svr4.c (enable_break): Pass down target.
	* spu-multiarch.c (parse_spufs_run): Pass down target.
	* spu-tdep.c (spu2ppu_sniffer): Pass down target.
	* target-delegates.c: Regenerate.
	* target.c (g_target_stack): Delete.
	(current_top_target): Return the current inferior's top target.
	(target_has_execution_1): Refer to the passed-in inferior's top
	target.
	(target_supports_terminal_ours): Check whether the initial
	inferior was already created.
	(decref_target): New.
	(target_stack::push): Incref/decref the target.
	(push_target, push_target, unpush_target): Adjust.
	(target_stack::unpush): Defref target.
	(target_is_pushed): Return bool.  Adjust to refer to the current
	inferior's target stack.
	(dispose_inferior): Delete, and inline parts ...
	(target_preopen): ... here.  Only dispose of the current inferior.
	(target_detach): Hold strong target reference while detaching.
	Pass target down.
	(target_thread_name): Add assertion.
	(target_resume): Pass down target.
	(target_ops::beneath, find_target_at): Adjust to refer to the
	current inferior's target stack.
	(get_dummy_target): New.
	(target_pass_ctrlc): Pass the Ctrl-C to the first inferior that
	has a thread running.
	(initialize_targets): Rename to ...
	(_initialize_target): ... this.
	* target.h: Include "gdbsupport/refcounted-object.h".
	(struct target_ops): Inherit refcounted_object.
	(target_ops::shortname, target_ops::longname): Make const.
	(target_ops::async_wait_fd): New method.
	(decref_target): Declare.
	(struct target_ops_ref_policy): New.
	(target_ops_ref): New typedef.
	(get_dummy_target): Declare function.
	(target_is_pushed): Return bool.
	* thread-iter.c (all_matching_threads_iterator::m_inf_matches)
	(all_matching_threads_iterator::all_matching_threads_iterator):
	Handle filter target.
	* thread-iter.h (struct all_matching_threads_iterator, struct
	all_matching_threads_range, class all_non_exited_threads_range):
	Filter by target too.  Remove explicit.
	* thread.c (threads_executing): Delete.
	(inferior_thread): Pass down current inferior.
	(clear_thread_inferior_resources): Pass down thread pointer
	instead of ptid_t.
	(add_thread_silent, add_thread_with_info, add_thread): Add
	process_stratum_target parameter.  Use it for thread and inferior
	searches.
	(is_current_thread): New.
	(thread_info::deletable): Use it.
	(find_thread_ptid, thread_count, in_thread_list)
	(thread_change_ptid, set_resumed, set_running): New
	process_stratum_target parameter.  Pass it down.
	(set_executing): New process_stratum_target parameter.  Pass it
	down.  Adjust reference to 'threads_executing'.
	(threads_are_executing): New process_stratum_target parameter.
	Adjust reference to 'threads_executing'.
	(set_stop_requested, finish_thread_state): New
	process_stratum_target parameter.  Pass it down.
	(switch_to_thread): Also match inferior.
	(switch_to_thread): New process_stratum_target parameter.  Pass it
	down.
	(update_threads_executing): Reimplement.
	* top.c (quit_force): Pop targets from all inferior.
	(gdb_init): Don't call initialize_targets.
	* windows-nat.c (windows_nat_target) <get_windows_debug_event>:
	Declare.
	(windows_add_thread, windows_delete_thread): Adjust.
	(get_windows_debug_event): Rename to ...
	(windows_nat_target::get_windows_debug_event): ... this.  Adjust.
	* tracefile-tfile.c (tfile_target_open): Pass down target.
	* gdbsupport/common-gdbthread.h (struct process_stratum_target):
	Forward declare.
	(switch_to_thread): Add process_stratum_target parameter.
	* mi/mi-interp.c (mi_on_resume_1): Add process_stratum_target
	parameter.  Use it.
	(mi_on_resume): Pass target down.
	* nat/fork-inferior.c (startup_inferior): Add
	process_stratum_target parameter.  Pass it down.
	* nat/fork-inferior.h (startup_inferior): Add
	process_stratum_target parameter.
	* python/py-threadevent.c (py_get_event_thread): Pass target down.

gdb/gdbserver/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* fork-child.c (post_fork_inferior): Pass target down to
	startup_inferior.
	* inferiors.c (switch_to_thread): Add process_stratum_target
	parameter.
	* lynx-low.c (lynx_target_ops): Now a process_stratum_target.
	* nto-low.c (nto_target_ops): Now a process_stratum_target.
	* linux-low.c (linux_target_ops): Now a process_stratum_target.
	* remote-utils.c (prepare_resume_reply): Pass the target to
	switch_to_thread.
	* target.c (the_target): Now a process_stratum_target.
	(done_accessing_memory): Pass the target to switch_to_thread.
	(set_target_ops): Ajust to use process_stratum_target.
	* target.h (struct target_ops): Rename to ...
	(struct process_stratum_target): ... this.
	(the_target, set_target_ops): Adjust.
	(prepare_to_access_memory): Adjust comment.
	* win32-low.c (child_xfer_memory): Adjust to use
	process_stratum_target.
	(win32_target_ops): Now a process_stratum_target.

Another bug exposed by gdb.server/extended-remote-restart.exp in the
multi-target work is that remote_target::start_remote can leave
inferior_ptid and current_inferior() out of sync:

 (top-gdb) p current_inferior_->pid
 $1 = 29541
 (top-gdb) p inferior_ptid
 $2 = {m_pid = 29540, m_lwp = 29540, m_tid = 0}

This is caused by writing to inferior_ptid directly instead of using
switch_to_thread.  Also, "inferior_list->thread_list->ptid" assumes
that we want the first thread of the first inferior, but that inferior
may not have threads, or with multi-target, that target may be
connected to some other target.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* remote.c (remote_target::start_remote): Don't set inferior_ptid
	directly.  Instead find the first thread in the thread list and
	use switch_to_thread.

The multi-target patch will change the remote target's behavior when:

- the current inferior is connected to an extended-remote target.
- the current inferior is attached to any process.
- some other inferior than than the current one is live.

In current master, we get:

 (gdb) tar extended-remote :9999
 A program is being debugged already.  Kill it? (y or n)

While after multi-target, since each inferior may have its own target
connection, we'll get:

 (gdb) tar extended-remote :9999
 Already connected to a remote target.  Disconnect? (y or n)

That change made gdb.server/extended-remote-restart.exp expose a gdb
bug, because it made "target remote", via gdb_reconnect, just
disconnect from the previous connection, while in current master that
command would kill the inferior before disconnecting.  In turn, that
would make a multi-target gdb find processes already running under
control of gdbserver as soon as it reconnects, while in current master
there is never any process around when gdb reconnects, since they'd
all been killed prior to disconnection.

The bug this exposed is that remote_target::remote_add_inferior was
always reusing current_inferior() for the new process, even if the
current inferior was already bound to a process.  In the testcase's
case, when we reconnect, the remote is debugging two processes.  So
we'd bind the first remote process to the empty current inferior the
first time, and then bind the second remote process to the same
inferior again, essencially losing track of the first process.  That
resulted in failed assertions when we look up the inferior for the
first process by PID.  The fix is to still prefer binding to the
current inferior (so that plain "target remote" keeps doing what you'd
expect), but not reuse the current inferior if it is already bound to
a process.

This patch tweaks the test to explicitly disconnect before
reconnecting, to avoid GDB killing processes, thus making current GDB
behave the same as it will behave when the multi-target work lands.
That change alone without the GDB fix exposes the bug like so:

 (gdb) PASS: gdb.server/extended-remote-restart.exp: kill: 0, follow-child 0: disconnect
 target extended-remote localhost:2350
 Remote debugging using localhost:2350
 src/gdb/thread.c:93: internal-error: thread_info* inferior_thread(): Assertion `tp' failed.
 A problem internal to GDB has been detected,
 further debugging may prove unreliable.
 Quit this debugging session? (y or n)

The original bug that the testcase was written for was related to
killing, (git 9d4a934c ("gdb: Fix assert for extended-remote
target (PR gdb/18050)")), but since the testcase tries reconnecting
with both explicitly killing and not explicitly killing, I think we're
covering the original bug with this testcase change.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* remote.c (remote_target::remote_add_inferior): Don't bind a
	process to the current inferior if the current inferior is already
	bound to a process.

gdb/testsuite/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdb.server/extended-remote-restart.exp (test_reload): Explicitly
	disconnect before reconnecting.

The multi-target patch makes inferior_ptid point to null_ptid before
calling into target_wait, which catches bad uses of inferior_ptid,
since the current selected thread in gdb shouldn't have much relation
to the thread that reports an event.

One such bad use is found in remote_target::remote_parse_stop_reply,
where we handle the 'W' or 'X' packets (process exit), and the remote
target does not support the multi-process extensions, i.e., it does
not report the PID of the process that exited.

With the multi-target patch, that would result in a failed assertion,
trying to find the inferior for process pid 0.

gdb/ChangeLog:
2020-01-10  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>
	    Pedro Alves	 <palves@redhat.com>

	* remote.c (remote_target::remote_parse_stop_reply) <W/X packets>:
	If no process is specified, return null_ptid instead of
	inferior_ptid.
	(remote_target::wait_as): Handle TARGET_WAITKIND_EXITED /
	TARGET_WAITKIND_SIGNALLED with no pid.

gdb/testsuite/ChangeLog:
2020-01-10  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>
	    Pedro Alves	 <palves@redhat.com>

	* gdb.server/connect-without-multi-process.exp: Also test
	continuing to end.

With current master, on a Fedora 27 machine with a kernel with buggy
watchpoint support, I see:

  (gdb) PASS: gdb.threads/watchpoint-fork.exp: parent: singlethreaded: hardware breakpoints work
  continue
  Continuing.
  warning: Remote failure reply: E01
  Remote communication error.  Target disconnected.: Connection reset by peer.
  (gdb) FAIL: gdb.threads/watchpoint-fork.exp: parent: singlethreaded: watchpoints work
  continue
  The program is not being run.
  (gdb) FAIL: gdb.threads/watchpoint-fork.exp: parent: singlethreaded: breakpoint after the first fork (the program is no longer running)

The FAILs themselves aren't what's interesting here.  What is
interesting is that with the main multi-target patch applied, I was getting this:

  (gdb) PASS: gdb.threads/watchpoint-fork.exp: parent: singlethreaded: hardware breakpoints work
  continue
  Continuing.
  warning: Remote failure reply: E01
  /home/pedro/brno/pedro/gdb/binutils-gdb-2/build/../src/gdb/inferior.c:285: internal-error: inferior* find_inferior_pid(process_stratum_target*, int): Assertion `pid != 0' failed.
  A problem internal to GDB has been detected,
  further debugging may prove unreliable.
  Quit this debugging session? (y or n) FAIL: gdb.threads/watchpoint-fork.exp: parent: singlethreaded: watchpoints work (GDB internal error)

The problem is that in remote_target::wait_as, we're hitting this:

  switch (buf[0])
    {
    case 'E':		/* Error of some sort.	*/
      /* We're out of sync with the target now.  Did it continue or
	 not?  Not is more likely, so report a stop.  */
      rs->waiting_for_stop_reply = 0;

      warning (_("Remote failure reply: %s"), buf);
      status->kind = TARGET_WAITKIND_STOPPED;
      status->value.sig = GDB_SIGNAL_0;
      break;

which leaves event_ptid as null_ptid.  At the end of the function, we then reach:

  else if (status->kind != TARGET_WAITKIND_EXITED
	   && status->kind != TARGET_WAITKIND_SIGNALLED)
    {
      if (event_ptid != null_ptid)
	record_currthread (rs, event_ptid);
      else
	event_ptid = inferior_ptid;                 <<<<< here
    }

and the trouble is that with the multi-target patch, we'll get here
with inferior_ptid as null_ptid too.  That is done exactly to find
these implicit assumptions that inferior_ptid is a good choice for
default thread, which isn't generaly true.

I first thought of fixing this in the "case 'E'" path, but, given that
this "event_ptid = inferior_ptid" path is also taken when the remote
target does not support threads at all, no thread-related packets or
extensions, it's better to fix it in latter path, to handle all
scenarios that miss reporting a thread.

That's what this patch does.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* remote.c (first_remote_resumed_thread): New.
	(remote_target::wait_as): Use it as default event_ptid instead of
	inferior_ptid.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* infrun.c (handle_no_resumed): Use all_non_exited_inferiors.

It's not possible to open a tfile target with an invalid trace_fd, and
it's not possible to close a closed target, so this early return is dead.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* tracefile-tfile.c (tfile_target::close): Assert that trace_fd is
	not -1.

- Make get_last_target_status arguments optional.  A following patch
  will add another argument to get_last_target_status (the event's
  target), and passing nullptr when we don't care for some piece of
  info is handier than creating dummy local variables.

- Declare nullify_last_target_wait_ptid in a header, and remove the
  local extern declaration from linux-fork.c.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* break-catch-sig.c (signal_catchpoint_print_it): Don't pass a
	ptid to get_last_target_status.
	* break-catch-syscall.c (print_it_catch_syscall): Don't pass a
	ptid to get_last_target_status.
	* infcmd.c (continue_command): Don't pass a target_waitstatus to
	get_last_target_status.
	(info_program_command): Don't pass a target_waitstatus to
	get_last_target_status.
	* infrun.c (init_wait_for_inferior): Use
	nullify_last_target_wait_ptid.
	(get_last_target_status): Handle nullptr arguments.
	(nullify_last_target_wait_ptid): Clear target_last_waitstatus.
	(print_stop_event): Don't pass a ptid to get_last_target_status.
	(normal_stop): Don't pass a ptid to get_last_target_status.
	* infrun.h (get_last_target_status, set_last_target_status): Move
	comments here and update.
	(nullify_last_target_wait_ptid): Declare.
	* linux-fork.c (fork_load_infrun_state): Remove local extern
	declaration of nullify_last_target_wait_ptid.
	* linux-nat.c (get_detach_signal): Don't pass a target_waitstatus
	to get_last_target_status.

Once each inferior has its own target stack, we'll need to make sure
that the right inferior is selected before we call into target
methods.

It kind of sounds worse than it is in practice.  Not that many places
need to be concerned.

In thread.c, we add a new switch_to_thread_if_alive function that
centralizes the switching before calls to target_thread_alive.  Other
cases are handled with explicit switching.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdbthread.h (scoped_restore_current_thread)
	<dont_restore, restore, m_dont_restore>: Declare.
	* thread.c (thread_alive): Add assertion.  Return bool.
	(switch_to_thread_if_alive): New.
	(prune_threads): Switch inferior/thread.
	(print_thread_info_1): Switch thread before calling target methods.
	(scoped_restore_current_thread::restore): New, factored out from
	...
	(scoped_restore_current_thread::~scoped_restore_current_thread):
	... this.
	(scoped_restore_current_thread::scoped_restore_current_thread):
	Add assertion.
	(thread_apply_all_command, thread_select): Use
	switch_to_thread_if_alive.
	* infrun.c (proceed, restart_threads, handle_signal_stop)
	(switch_back_to_stepped_thread): Switch current thread before
	calling target methods.

Several places want to switch context to an inferior and its pspace,
while at the same time switch to "no thread selected".  This commit
adds a function that does that, and uses it in a few places.

gdb/ChangeLog:
2020-01-10  Pedro Alves <palves@redhat.com>

	* inferior.c (switch_to_inferior_no_thread): New function,
	factored out from ...
	(inferior_command): ... here.
	* inferior.h (switch_to_inferior_no_thread): Declare.
	* mi/mi-main.c (run_one_inferior): Use
	switch_to_inferior_no_thread.

I believe this comment:

      /* Killing off the inferior can leave us with a core file.  If
	 so, print the state we are left in.  */

Referred to the fact that a decade ago, by design, GDB would let you
type "run" when debugging a core dump, keeping the core open.  That
"run" would push a process_stratum target on the target stack for the
live process, and, the core would remain open -- we used to have a
core_stratum.  When the live process was killed/detached or exited,
GDB would go back to debugging the core, since the core_stratum target
was now at the top of the stack.  That design had a number of
problems, see here for example:

  https://sourceware.org/ml/gdb-patches/2008-08/msg00290.html

In 2010, core_stratum was finaly eliminated and cores now have
process_stratum too, with commit c0edd9ed ("Make core files the
process_stratum.").  Pushing a live process on the stack while you're
debugging a core discards the core completely.

I also thought that this might be in use with checkpoints, but it does
not -- "kill" when you have multiple checkpoints kills all the
checkpoints.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* infcmd.c (kill_command): Remove dead code.

I believe the tail end of remote_target::mourn_inferior is broken, and
it's been broken for too long to even bother trying to fix.  Most
probably nobody needs it.  If the code is reached and we find the
target is running, we'd need to resync the thread list, at least,
since generic_mourn_inferior got rid of all the threads in the
inferior, otherwise, we'd hit an assertion on the next call to
inferior_thread(), for example.  A "correct" fix would probably
involve restarting the whole remote_target::start_remote requence,
exactly as if we had completely disconnected and reconnected from
scratch.

Note that regular stub debugging usually uses plain target remote, but
this code is only reachable in target extended-mode:

- The !remote_multi_process_p check means that it's only reacheable if
  the stub does not support multi-process.  I.e., there can only ever
  be one live process.

- remote_target::mourn_inferior has this at the top:

  /* In 'target remote' mode with one inferior, we close the connection.  */
  if (!rs->extended && number_of_live_inferiors () <= 1)
    {
      unpush_target (this);

      /* remote_close takes care of doing most of the clean up.  */
      generic_mourn_inferior ();
      return;
    }

  Which means that if we only had one live inferior (which for our
  case, must be true), we'll have closed the connection already,
  unless we're in extended-remote mode.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* remote.c (remote_target::mourn_inferior): No longer check
	whether the target is running.

With the multi-target work, each inferior will have its own target
stack, so to call a target method, we'll need to make sure that the
inferior in question is the current one, otherwise target->beneath()
calls will find the target beneath in the wrong inferior.

In some places, it's much more convenient to be able to check whether
an inferior has execution without having to switch to it in order to
call target_has_execution on the right inferior/target stack, to avoid
side effects with switching inferior/thread/program space.

The current target_ops::has_execution method takes a ptid_t as
parameter, which, in a multi-target world, isn't sufficient to
identify the target.  This patch prepares to address that, by changing
the parameter to an inferior pointer instead.  From the inferior,
we'll be able to query its target stack to tell which target is
beneath.

Also adds a new inferior::has_execution() method to make callers a bit
more natural to read.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* corelow.c (core_target::has_execution): Change parameter type to
	inferior pointer.
	* inferior.c (number_of_live_inferiors): Use
	inferior::has_execution instead of target_has_execution_1.
	* inferior.h (inferior::has_execution): New.
	* linux-thread-db.c (thread_db_target::update_thread_list): Use
	inferior::has_execution instead of target_has_execution_1.
	* process-stratum-target.c
	(process_stratum_target::has_execution): Change parameter type to
	inferior pointer.  Check the inferior's PID instead of
	inferior_ptid.
	* process-stratum-target.h
	(process_stratum_target::has_execution): Change parameter type to
	inferior pointer.
	* record-full.c (record_full_core_target::has_execution): Change
	parameter type to inferior pointer.
	* target.c (target_has_execution_1): Change parameter type to
	inferior pointer.
	(target_has_execution_current): Adjust.
	* target.h (target_ops::has_execution): Change parameter type to
	inferior pointer.
	(target_has_execution_1): Change parameter type to inferior
	pointer.  Change return type to bool.
	* tracefile.h (tracefile_target::has_execution): Change parameter
	type to inferior pointer.

Commit 20f0d60d ("Avoid crash when calling warning too early"),
added a "current_top_target () != NULL" check to
target_supports_terminal_ours, so this check in exceptions.c is now
obsolete.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* exceptions.c (print_flush): Remove current_top_target() check.

The "set remote exec-file" setting is per-inferior, but the "show
remote exec-file" command always shows the last set exec-file,
irrespective of the current inferior.  E.g.:

 # Set inferior 1's exec-file:
 (gdb) set remote exec-file prog1

 # Add inferior 2, switch to it, and set its exec-file:
 (gdb) add-inferior
 Added inferior 2
 (gdb) inferior 2
 (gdb) set remote exec-file prog2

 # Switch back to inferior 1, and show its exec-file:
 (gdb) inferior 1
 (gdb) show remote exec-file
 prog2
 ^^^^^ should show "prog1" instead here.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* remote.c (show_remote_exec_file): Show the current inferior's
	exec-file instead of the command variable's value.

gdb/testsuite/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdb.base/remote-exec-file.exp: New file.

The multi-target patch sets inferior_ptid to null_ptid before handling
a target event, and thus before calling target_wait, in order to catch
places in target_ops::wait implementations that are incorrectly
relying on inferior_ptid (which could otherwise be a ptid of a
different target, for example).  That caught this instance in
record-full.c.

Fix it by saving the last resumed ptid, and then using it in
record_full_wait_1, just like how the last "step" argument passed to
record_full_target::resume is handled too.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* record-full.c (record_full_resume_ptid): New global.
	(record_full_target::resume): Set it.
	(record_full_wait_1): Use record_full_resume_ptid instead of
	inferior_ptid.

In non-stop mode, if you resume the program in the background (with
"continue&", for example), then gdb makes sure to not switch the
current thread behind your back.  That means that you can be sure that
the commands you type apply to the thread you selected, even if some
other thread that was running in the background hits some event just
while you're typing.

In all-stop mode, however, if you resume the program in the
background, gdb let's the current thread switch behind your back.

This is bogus, of course.  All-stop and non-stop background
resumptions should behave the same.

This patch fixes that, and adds a testcase that exposes the bad
behavior in current master.

The fork-running-state.exp changes are necessary because that
preexisting testcase was expecting the old behavior:

Before:

  continue &
  Continuing.
  (gdb)
  [Attaching after process 8199 fork to child process 8203]
  [New inferior 2 (process 8203)]
  info threads
    Id   Target Id                      Frame
    1.1  process 8199 "fork-running-st" (running)
  * 2.1  process 8203 "fork-running-st" (running)
  (gdb)

After:

  continue &
  Continuing.
  (gdb)
  [Attaching after process 24660 fork to child process 24664]
  [New inferior 2 (process 24664)]
  info threads
    Id   Target Id                       Frame
  * 1.1  process 24660 "fork-running-st" (running)
    2.1  process 24664 "fork-running-st" (running)
  (gdb)

Here we see that before this patch GDB switches current inferior to
the new inferior behind the user's back, as a side effect of handling
the fork.

The delete_exited_threads call in inferior_appeared is there to fix an
issue that Baris found in a previous version of this patch.  The
fetch_inferior_event change increases the refcount of the current
thread, and in case the fetched inferior event denotes a thread exit,
the thread will not be deleted right away.  A non-deleted but exited
thread stays in the inferior's thread list.  This, in turn, causes the
"init_thread_list" call in inferior.c to be skipped.  A consequence is
that the global thread ID counter is not restarted if the current
thread exits, and then the inferior is restarted:

 (gdb) start
 Temporary breakpoint 1 at 0x4004d6: file main.c, line 21.
 Starting program: /tmp/main

 Temporary breakpoint 1, main () at main.c:21
 21        foo ();
 (gdb) info threads -gid
   Id   GId  Target Id            Frame
 * 1    1    process 16106 "main" main () at main.c:21
 (gdb) c
 Continuing.
 [Inferior 1 (process 16106) exited normally]
 (gdb) start
 Temporary breakpoint 2 at 0x4004d6: file main.c, line 21.
 Starting program: /tmp/main

 Temporary breakpoint 2, main () at main.c:21
 21        foo ();
 (gdb) info threads -gid
   Id   GId  Target Id            Frame
 * 1    2    process 16138 "main" main () at main.c:21
       ^^^

Notice that GId == 2 above.  It should have been "1" instead.

The new tids-git-reset.exp testcase exercises the problem above.

gdb/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdbthread.h (scoped_restore_current_thread)
	<dont_restore, restore, m_dont_restore>: Declare.
	* thread.c (thread_alive): Add assertion.  Return bool.
	(switch_to_thread_if_alive): New.
	(prune_threads): Switch inferior/thread.
	(print_thread_info_1): Switch thread before calling target methods.
	(scoped_restore_current_thread::restore): New, factored out from
	...
	(scoped_restore_current_thread::~scoped_restore_current_thread):
	... this.
	(scoped_restore_current_thread::scoped_restore_current_thread):
	Add assertion.
	(thread_apply_all_command, thread_select): Use
	switch_to_thread_if_alive.

gdb/testsuite/ChangeLog:
2020-01-10  Pedro Alves  <palves@redhat.com>

	* gdb.base/fork-running-state.exp (do_test): Adjust expected
	output.
	* gdb.threads/async.c: New.
	* gdb.threads/async.exp: New.
	* gdb.multi/tids-gid-reset.c: New.
	* gdb.multi/tids-gid-reset.exp: New.

According to the SystemTap documentation on user-space probes[0], stap
probe points without semaphores are denoted by setting the semaphore
address in the probe's note to zero. At present the code does do a
comparison of the semaphore address against zero, but only after it's
been relocated; as such it will (almost?) always fail, commonly
resulting in GDB trying to overwrite the ELF magic located at the
image's base address.

This commit tests the address as specified in the SDT note rather than
the relocated value in order to correctly detect absent probe
semaphores.

[0]: https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation

gdb/Changelog:
2020-01-11  George Barrett  <bob@bob131.so>

	* stap-probe.c (stap_modify_semaphore): Don't check for null
	semaphores.
	(stap_probe::set_semaphore, stap_probe::clear_semaphore): Check
	for null semaphores.

gdb/testsuite/ChangeLog:
2020-01-11  George Barrett  <bob@bob131.so>

	* gdb.base/stap-probe.c (relocation_marker): Add dummy variable
	to help in finding the image relocation offset.
	* gdb.base/stap-probe.exp (stap_test): Accept arbitrary compile
	options in arguments.
	(stap_test_no_debuginfo): Likewise.
	(stap-probe-nosem-noopt-pie, stap-probe-nosem-noopt-nopie): Add
	test variants.
	(stap_test): Add null semaphore relocation test.

This patch resolves a couple of issues with the test case for SystemTap
user-space probe points:
  1. The preprocessor macro guarding the semaphore variables in the C
     file is (rather confusingly) named USE_PROBES. This has been
     renamed to USE_SEMAPHORES, to better reflect its function.
  2. The test procedures in the expect file improperly pass the flag
     defining USE_PROBES to prepare_for_testing; as such, the test
     binary that's supposed to have probes with semaphores is the same
     as the one without. This has also been fixed.
  3. No test is performed to check that `info probes' returns
     information about probe semaphores. Such a test is included in this
     patch.

gdb/testsuite/ChangeLog
2020-01-10  George Barrett  <bob@bob131.so>

	* gdb.base/stap-probe.c: Rename USE_PROBES to USE_SEMAPHORES.
	* gdb.base/stap-probe.exp: Likewise.
	(stap_test): Pass argument as an additional flag.
	(stap_test_no_debuginfo): Likewise.
	(stap_test): Check `info probes stap' output for semaphore
	addresses if the test binary is supposed to have them.

With static PIE linking undefined weak symbols are resolved to 0, so no
dynamic relocation is needed for them. The UNDEFWEAK_NO_DYNAMIC_RELOC
macro was introduced so this case can be handled easily, but it was not
applied consistently in the first attempt to fix ld/22269 for arm:

  commit 95b03e4a
  arm: Check UNDEFWEAK_NO_DYNAMIC_RELOC

This patch fixes spurious relative relocs in static PIE binaries against
GOT entries created for undefined weak symbols on arm*-*, this fixes

FAIL: pr22269-1 (static pie undefined weak)

bfd/ChangeLog:

	PR ld/22269
	* elf32-arm.c (elf32_arm_final_link_relocate): Use
	UNDEFWEAK_NO_DYNAMIC_RELOC.
	(allocate_dynrelocs_for_symbol): Likewise.

This changes the fix to PR 25210 by removing the ELF class change.
As it turns out the correct change was only the change in compress.c.

Everything else is unneeded and setting the elf class is making the linker
behave very oddly under LTO.  The first stub is correctly written out but for
the rest the suddenly don't have a pointer to the stub section anymore.

This caused SPEC to fail as the program would branch to the stub and it wouldn't
be filled in.

Committed to master under the trivial rule as this is partially reverting a previous commit.

bfd/ChangeLog:

	PR 25210
	* elfnn-aarch64.c (_bfd_aarch64_create_stub_section): Remove elfclass.

	* testsuite/gas/elf/pr14891.s: Don't start directives in first column.
	* testsuite/gas/elf/pr21661.d: Don't run on hpux.