Change iterate_over_lwps to take a gdb::function_view

This changes iterate_over_lwps to use a gdb::function_view.  This was
needed in order to make null_ptid and minus_one_ptid 'const'.

gdb/ChangeLog
2019-03-12  Tom Tromey  <tromey@adacore.com>

	* linux-nat.c (iterate_over_lwps): Update.
	(stop_callback): Remove parameter.
	(stop_wait_callback, detach_callback, resume_set_callback)
	(select_singlestep_lwp_callback, set_ignore_sigint)
	(status_callback, resumed_callback, resume_clear_callback)
	(kill_callback, kill_wait_callback, linux_nat_stop_lwp): Remove
	data parameter.
	(linux_nat_target::detach, linux_nat_target::resume)
	(linux_stop_and_wait_all_lwps, select_event_lwp)
	(linux_nat_filter_event, linux_nat_wait_1)
	(linux_nat_target::kill, linux_nat_target::stop)
	(linux_nat_target::stop): Update.
	(linux_nat_resume_callback): Change type.
	(resume_stopped_resumed_lwps, count_events_callback)
	(select_event_lwp_callback): Likewise.
	(linux_stop_lwp, linux_nat_stop_lwp): Update.
	* arm-linux-nat.c (struct update_registers_data): Remove.
	(update_registers_callback): Change type.
	(arm_linux_insert_hw_breakpoint1): Update.
	* nat/x86-linux-dregs.c (update_debug_registers_callback): Remove
	parameter.
	(x86_linux_dr_set_addr): Update.
	(x86_linux_dr_set_control): Update.
	* nat/linux-nat.h (iterate_over_lwps_ftype): Remove parameter.
	(iterate_over_lwps): Use gdb::function_view.
	* nat/aarch64-linux-hw-point.c (struct
	aarch64_dr_update_callback_param): Remove.
	(debug_reg_change_callback): Change type.
	(aarch64_notify_debug_reg_change): Update.
	* s390-linux-nat.c (s390_refresh_per_info): Update.

gdb/gdbserver/ChangeLog
2019-03-12  Tom Tromey  <tromey@adacore.com>

	* linux-low.c (iterate_over_lwps): Update.

9 files changed, 143 insertions, 109 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ee9fabe..5e9beb9 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,36 @@
+2019-03-12  Tom Tromey  <tromey@adacore.com>
+
+	* linux-nat.c (iterate_over_lwps): Update.
+	(stop_callback): Remove parameter.
+	(stop_wait_callback, detach_callback, resume_set_callback)
+	(select_singlestep_lwp_callback, set_ignore_sigint)
+	(status_callback, resumed_callback, resume_clear_callback)
+	(kill_callback, kill_wait_callback, linux_nat_stop_lwp): Remove
+	data parameter.
+	(linux_nat_target::detach, linux_nat_target::resume)
+	(linux_stop_and_wait_all_lwps, select_event_lwp)
+	(linux_nat_filter_event, linux_nat_wait_1)
+	(linux_nat_target::kill, linux_nat_target::stop)
+	(linux_nat_target::stop): Update.
+	(linux_nat_resume_callback): Change type.
+	(resume_stopped_resumed_lwps, count_events_callback)
+	(select_event_lwp_callback): Likewise.
+	(linux_stop_lwp, linux_nat_stop_lwp): Update.
+	* arm-linux-nat.c (struct update_registers_data): Remove.
+	(update_registers_callback): Change type.
+	(arm_linux_insert_hw_breakpoint1): Update.
+	* nat/x86-linux-dregs.c (update_debug_registers_callback): Remove
+	parameter.
+	(x86_linux_dr_set_addr): Update.
+	(x86_linux_dr_set_control): Update.
+	* nat/linux-nat.h (iterate_over_lwps_ftype): Remove parameter.
+	(iterate_over_lwps): Use gdb::function_view.
+	* nat/aarch64-linux-hw-point.c (struct
+	aarch64_dr_update_callback_param): Remove.
+	(debug_reg_change_callback): Change type.
+	(aarch64_notify_debug_reg_change): Update.
+	* s390-linux-nat.c (s390_refresh_per_info): Update.
+
 2019-03-11  Tom Tromey  <tromey@adacore.com>
 
 	* dwarf2read.c (dwarf2_find_containing_comp_unit): Remove
diff --git a/gdb/arm-linux-nat.c b/gdb/arm-linux-nat.c
index e4622b0..8c98a71 100644
--- a/gdb/arm-linux-nat.c
+++ b/gdb/arm-linux-nat.c
@@ -952,26 +952,18 @@ arm_linux_hw_breakpoint_equal (const struct arm_linux_hw_breakpoint *p1,
 /* Callback to mark a watch-/breakpoint to be updated in all threads of
    the current process.  */
 
-struct update_registers_data
-{
-  int watch;
-  int index;
-};
-
 static int
-update_registers_callback (struct lwp_info *lwp, void *arg)
+update_registers_callback (struct lwp_info *lwp, int watch, int index)
 {
-  struct update_registers_data *data = (struct update_registers_data *) arg;
-
   if (lwp->arch_private == NULL)
     lwp->arch_private = XCNEW (struct arch_lwp_info);
 
   /* The actual update is done later just before resuming the lwp,
      we just mark that the registers need updating.  */
-  if (data->watch)
-    lwp->arch_private->wpts_changed[data->index] = 1;
+  if (watch)
+    lwp->arch_private->wpts_changed[index] = 1;
   else
-    lwp->arch_private->bpts_changed[data->index] = 1;
+    lwp->arch_private->bpts_changed[index] = 1;
 
   /* If the lwp isn't stopped, force it to momentarily pause, so
      we can update its breakpoint registers.  */
@@ -991,7 +983,6 @@ arm_linux_insert_hw_breakpoint1 (const struct arm_linux_hw_breakpoint* bpt,
   ptid_t pid_ptid;
   gdb_byte count, i;
   struct arm_linux_hw_breakpoint* bpts;
-  struct update_registers_data data;
 
   pid = inferior_ptid.pid ();
   pid_ptid = ptid_t (pid);
@@ -1010,10 +1001,13 @@ arm_linux_insert_hw_breakpoint1 (const struct arm_linux_hw_breakpoint* bpt,
   for (i = 0; i < count; ++i)
     if (!arm_hwbp_control_is_enabled (bpts[i].control))
       {
-        data.watch = watchpoint;
-        data.index = i;
         bpts[i] = *bpt;
-        iterate_over_lwps (pid_ptid, update_registers_callback, &data);
+        iterate_over_lwps (pid_ptid,
+			   [=] (struct lwp_info *info)
+			   {
+			     return update_registers_callback (info, watch,
+							       index);
+			   });
         break;
       }
 
diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 447b908..3eb9ec0 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,7 @@
+2019-03-12  Tom Tromey  <tromey@adacore.com>
+
+	* linux-low.c (iterate_over_lwps): Update.
+
 2019-03-06  Tom Tromey  <tom@tromey.com>
 
 	* server.c (detach_or_kill_for_exit_cleanup): Remove parameter.
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 8c5a51f..b1a9d12 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -1843,14 +1843,13 @@ num_lwps (int pid)
 
 struct lwp_info *
 iterate_over_lwps (ptid_t filter,
-		   iterate_over_lwps_ftype callback,
-		   void *data)
+		   gdb::function_view<iterate_over_lwps_ftype> callback)
 {
   thread_info *thread = find_thread (filter, [&] (thread_info *thr_arg)
     {
       lwp_info *lwp = get_thread_lwp (thr_arg);
 
-      return callback (lwp, data);
+      return callback (lwp);
     });
 
   if (thread == NULL)
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 063afe2..ad5ec3d 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -262,8 +262,7 @@ async_file_mark (void)
 
 static int kill_lwp (int lwpid, int signo);
 
-static int stop_callback (struct lwp_info *lp, void *data);
-static int resume_stopped_resumed_lwps (struct lwp_info *lp, void *data);
+static int stop_callback (struct lwp_info *lp);
 
 static void block_child_signals (sigset_t *prev_mask);
 static void restore_child_signals_mask (sigset_t *prev_mask);
@@ -807,8 +806,8 @@ linux_nat_target::pass_signals
 
 
 /* Prototypes for local functions.  */
-static int stop_wait_callback (struct lwp_info *lp, void *data);
-static int resume_stopped_resumed_lwps (struct lwp_info *lp, void *data);
+static int stop_wait_callback (struct lwp_info *lp);
+static int resume_stopped_resumed_lwps (struct lwp_info *lp, const ptid_t wait_ptid);
 static int check_ptrace_stopped_lwp_gone (struct lwp_info *lp);
 
 
@@ -960,8 +959,7 @@ find_lwp_pid (ptid_t ptid)
 
 struct lwp_info *
 iterate_over_lwps (ptid_t filter,
-		   iterate_over_lwps_ftype callback,
-		   void *data)
+		   gdb::function_view<iterate_over_lwps_ftype> callback)
 {
   struct lwp_info *lp, *lpnext;
 
@@ -971,7 +969,7 @@ iterate_over_lwps (ptid_t filter,
 
       if (lp->ptid.matches (filter))
 	{
-	  if ((*callback) (lp, data) != 0)
+	  if (callback (lp) != 0)
 	    return lp;
 	}
     }
@@ -1456,7 +1454,7 @@ detach_one_lwp (struct lwp_info *lp, int *signo_p)
 }
 
 static int
-detach_callback (struct lwp_info *lp, void *data)
+detach_callback (struct lwp_info *lp)
 {
   /* We don't actually detach from the thread group leader just yet.
      If the thread group exits, we must reap the zombie clone lwps
@@ -1477,12 +1475,12 @@ linux_nat_target::detach (inferior *inf, int from_tty)
 
   /* Stop all threads before detaching.  ptrace requires that the
      thread is stopped to sucessfully detach.  */
-  iterate_over_lwps (ptid_t (pid), stop_callback, NULL);
+  iterate_over_lwps (ptid_t (pid), stop_callback);
   /* ... and wait until all of them have reported back that
      they're no longer running.  */
-  iterate_over_lwps (ptid_t (pid), stop_wait_callback, NULL);
+  iterate_over_lwps (ptid_t (pid), stop_wait_callback);
 
-  iterate_over_lwps (ptid_t (pid), detach_callback, NULL);
+  iterate_over_lwps (ptid_t (pid), detach_callback);
 
   /* Only the initial process should be left right now.  */
   gdb_assert (num_lwps (pid) == 1);
@@ -1646,7 +1644,7 @@ resume_lwp (struct lwp_info *lp, int step, enum gdb_signal signo)
    Resume LWP with the last stop signal, if it is in pass state.  */
 
 static int
-linux_nat_resume_callback (struct lwp_info *lp, void *except)
+linux_nat_resume_callback (struct lwp_info *lp, struct lwp_info *except)
 {
   enum gdb_signal signo = GDB_SIGNAL_0;
 
@@ -1670,7 +1668,7 @@ linux_nat_resume_callback (struct lwp_info *lp, void *except)
 }
 
 static int
-resume_clear_callback (struct lwp_info *lp, void *data)
+resume_clear_callback (struct lwp_info *lp)
 {
   lp->resumed = 0;
   lp->last_resume_kind = resume_stop;
@@ -1678,7 +1676,7 @@ resume_clear_callback (struct lwp_info *lp, void *data)
 }
 
 static int
-resume_set_callback (struct lwp_info *lp, void *data)
+resume_set_callback (struct lwp_info *lp)
 {
   lp->resumed = 1;
   lp->last_resume_kind = resume_continue;
@@ -1705,7 +1703,7 @@ linux_nat_target::resume (ptid_t ptid, int step, enum gdb_signal signo)
 		 || ptid.is_pid ());
 
   /* Mark the lwps we're resuming as resumed.  */
-  iterate_over_lwps (ptid, resume_set_callback, NULL);
+  iterate_over_lwps (ptid, resume_set_callback);
 
   /* See if it's the current inferior that should be handled
      specially.  */
@@ -1766,7 +1764,10 @@ linux_nat_target::resume (ptid_t ptid, int step, enum gdb_signal signo)
     }
 
   if (resume_many)
-    iterate_over_lwps (ptid, linux_nat_resume_callback, lp);
+    iterate_over_lwps (ptid, [=] (struct lwp_info *info)
+			     {
+			       return linux_nat_resume_callback (info, lp);
+			     });
 
   if (debug_linux_nat)
     fprintf_unfiltered (gdb_stdlog,
@@ -2305,7 +2306,7 @@ wait_lwp (struct lwp_info *lp)
 /* Send a SIGSTOP to LP.  */
 
 static int
-stop_callback (struct lwp_info *lp, void *data)
+stop_callback (struct lwp_info *lp)
 {
   if (!lp->stopped && !lp->signalled)
     {
@@ -2339,7 +2340,7 @@ stop_callback (struct lwp_info *lp, void *data)
 void
 linux_stop_lwp (struct lwp_info *lwp)
 {
-  stop_callback (lwp, NULL);
+  stop_callback (lwp);
 }
 
 /* See linux-nat.h  */
@@ -2348,11 +2349,11 @@ void
 linux_stop_and_wait_all_lwps (void)
 {
   /* Stop all LWP's ...  */
-  iterate_over_lwps (minus_one_ptid, stop_callback, NULL);
+  iterate_over_lwps (minus_one_ptid, stop_callback);
 
   /* ... and wait until all of them have reported back that
      they're no longer running.  */
-  iterate_over_lwps (minus_one_ptid, stop_wait_callback, NULL);
+  iterate_over_lwps (minus_one_ptid, stop_wait_callback);
 }
 
 /* See linux-nat.h  */
@@ -2361,7 +2362,10 @@ void
 linux_unstop_all_lwps (void)
 {
   iterate_over_lwps (minus_one_ptid,
-		     resume_stopped_resumed_lwps, &minus_one_ptid);
+		     [] (struct lwp_info *info)
+		     {
+		       return resume_stopped_resumed_lwps (info, minus_one_ptid);
+		     });
 }
 
 /* Return non-zero if LWP PID has a pending SIGINT.  */
@@ -2383,7 +2387,7 @@ linux_nat_has_pending_sigint (int pid)
 /* Set a flag in LP indicating that we should ignore its next SIGINT.  */
 
 static int
-set_ignore_sigint (struct lwp_info *lp, void *data)
+set_ignore_sigint (struct lwp_info *lp)
 {
   /* If a thread has a pending SIGINT, consume it; otherwise, set a
      flag to consume the next one.  */
@@ -2484,7 +2488,7 @@ linux_nat_target::low_status_is_event (int status)
 /* Wait until LP is stopped.  */
 
 static int
-stop_wait_callback (struct lwp_info *lp, void *data)
+stop_wait_callback (struct lwp_info *lp)
 {
   struct inferior *inf = find_inferior_ptid (lp->ptid);
 
@@ -2516,7 +2520,7 @@ stop_wait_callback (struct lwp_info *lp, void *data)
 				target_pid_to_str (lp->ptid),
 				errno ? safe_strerror (errno) : "OK");
 
-	  return stop_wait_callback (lp, NULL);
+	  return stop_wait_callback (lp);
 	}
 
       maybe_clear_ignore_sigint (lp);
@@ -2566,7 +2570,7 @@ stop_wait_callback (struct lwp_info *lp, void *data)
    caused the stop became uninteresting.  */
 
 static int
-status_callback (struct lwp_info *lp, void *data)
+status_callback (struct lwp_info *lp)
 {
   /* Only report a pending wait status if we pretend that this has
      indeed been resumed.  */
@@ -2628,10 +2632,8 @@ status_callback (struct lwp_info *lp, void *data)
 /* Count the LWP's that have had events.  */
 
 static int
-count_events_callback (struct lwp_info *lp, void *data)
+count_events_callback (struct lwp_info *lp, int *count)
 {
-  int *count = (int *) data;
-
   gdb_assert (count != NULL);
 
   /* Select only resumed LWPs that have an event pending.  */
@@ -2644,7 +2646,7 @@ count_events_callback (struct lwp_info *lp, void *data)
 /* Select the LWP (if any) that is currently being single-stepped.  */
 
 static int
-select_singlestep_lwp_callback (struct lwp_info *lp, void *data)
+select_singlestep_lwp_callback (struct lwp_info *lp)
 {
   if (lp->last_resume_kind == resume_step
       && lp->status != 0)
@@ -2667,10 +2669,8 @@ lwp_status_pending_p (struct lwp_info *lp)
 /* Select the Nth LWP that has had an event.  */
 
 static int
-select_event_lwp_callback (struct lwp_info *lp, void *data)
+select_event_lwp_callback (struct lwp_info *lp, int *selector)
 {
-  int *selector = (int *) data;
-
   gdb_assert (selector != NULL);
 
   /* Select only resumed LWPs that have an event pending.  */
@@ -2869,8 +2869,7 @@ select_event_lwp (ptid_t filter, struct lwp_info **orig_lp, int *status)
      signal.  */
   if (!target_is_non_stop_p ())
     {
-      event_lp = iterate_over_lwps (filter,
-				    select_singlestep_lwp_callback, NULL);
+      event_lp = iterate_over_lwps (filter, select_singlestep_lwp_callback);
       if (event_lp != NULL)
 	{
 	  if (debug_linux_nat)
@@ -2885,7 +2884,11 @@ select_event_lwp (ptid_t filter, struct lwp_info **orig_lp, int *status)
       /* Pick one at random, out of those which have had events.  */
 
       /* First see how many events we have.  */
-      iterate_over_lwps (filter, count_events_callback, &num_events);
+      iterate_over_lwps (filter,
+			 [&] (struct lwp_info *info)
+			 {
+			   return count_events_callback (info, &num_events);
+			 });
       gdb_assert (num_events > 0);
 
       /* Now randomly pick a LWP out of those that have had
@@ -2898,9 +2901,14 @@ select_event_lwp (ptid_t filter, struct lwp_info **orig_lp, int *status)
 			    "SEL: Found %d events, selecting #%d\n",
 			    num_events, random_selector);
 
-      event_lp = iterate_over_lwps (filter,
-				    select_event_lwp_callback,
-				    &random_selector);
+      event_lp
+	= (iterate_over_lwps
+	   (filter,
+	    [&] (struct lwp_info *info)
+	    {
+	      return select_event_lwp_callback (info,
+						&random_selector);
+	    }));
     }
 
   if (event_lp != NULL)
@@ -2917,7 +2925,7 @@ select_event_lwp (ptid_t filter, struct lwp_info **orig_lp, int *status)
 /* Return non-zero if LP has been resumed.  */
 
 static int
-resumed_callback (struct lwp_info *lp, void *data)
+resumed_callback (struct lwp_info *lp)
 {
   return lp->resumed;
 }
@@ -3136,8 +3144,7 @@ linux_nat_filter_event (int lwpid, int status)
 		 will receive it - unless they're using CLONE_THREAD to
 		 share signals.  Since we only want to report it once, we
 		 mark it as ignored for all LWPs except this one.  */
-	      iterate_over_lwps (ptid_t (lp->ptid.pid ()),
-					      set_ignore_sigint, NULL);
+	      iterate_over_lwps (ptid_t (lp->ptid.pid ()), set_ignore_sigint);
 	      lp->ignore_sigint = 0;
 	    }
 	  else
@@ -3279,7 +3286,7 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
   block_child_signals (&prev_mask);
 
   /* First check if there is a LWP with a wait status pending.  */
-  lp = iterate_over_lwps (ptid, status_callback, NULL);
+  lp = iterate_over_lwps (ptid, status_callback);
   if (lp != NULL)
     {
       if (debug_linux_nat)
@@ -3336,11 +3343,14 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
       /* Now that we've pulled all events out of the kernel, resume
 	 LWPs that don't have an interesting event to report.  */
       iterate_over_lwps (minus_one_ptid,
-			 resume_stopped_resumed_lwps, &minus_one_ptid);
+			 [] (struct lwp_info *info)
+			 {
+			   return resume_stopped_resumed_lwps (info, minus_one_ptid);
+			 });
 
       /* ... and find an LWP with a status to report to the core, if
 	 any.  */
-      lp = iterate_over_lwps (ptid, status_callback, NULL);
+      lp = iterate_over_lwps (ptid, status_callback);
       if (lp != NULL)
 	break;
 
@@ -3350,7 +3360,7 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
 
       /* If there are no resumed children left, bail.  We'd be stuck
 	 forever in the sigsuspend call below otherwise.  */
-      if (iterate_over_lwps (ptid, resumed_callback, NULL) == NULL)
+      if (iterate_over_lwps (ptid, resumed_callback) == NULL)
 	{
 	  if (debug_linux_nat)
 	    fprintf_unfiltered (gdb_stdlog, "LLW: exit (no resumed LWP)\n");
@@ -3388,11 +3398,11 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
   if (!target_is_non_stop_p ())
     {
       /* Now stop all other LWP's ...  */
-      iterate_over_lwps (minus_one_ptid, stop_callback, NULL);
+      iterate_over_lwps (minus_one_ptid, stop_callback);
 
       /* ... and wait until all of them have reported back that
 	 they're no longer running.  */
-      iterate_over_lwps (minus_one_ptid, stop_wait_callback, NULL);
+      iterate_over_lwps (minus_one_ptid, stop_wait_callback);
     }
 
   /* If we're not waiting for a specific LWP, choose an event LWP from
@@ -3431,11 +3441,11 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
     {
       /* In all-stop, from the core's perspective, all LWPs are now
 	 stopped until a new resume action is sent over.  */
-      iterate_over_lwps (minus_one_ptid, resume_clear_callback, NULL);
+      iterate_over_lwps (minus_one_ptid, resume_clear_callback);
     }
   else
     {
-      resume_clear_callback (lp, NULL);
+      resume_clear_callback (lp);
     }
 
   if (linux_target->low_status_is_event (status))
@@ -3485,10 +3495,8 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
    to report, but are resumed from the core's perspective.  */
 
 static int
-resume_stopped_resumed_lwps (struct lwp_info *lp, void *data)
+resume_stopped_resumed_lwps (struct lwp_info *lp, const ptid_t wait_ptid)
 {
-  ptid_t *wait_ptid_p = (ptid_t *) data;
-
   if (!lp->stopped)
     {
       if (debug_linux_nat)
@@ -3522,7 +3530,7 @@ resume_stopped_resumed_lwps (struct lwp_info *lp, void *data)
 
 	  /* Don't bother if there's a breakpoint at PC that we'd hit
 	     immediately, and we're not waiting for this LWP.  */
-	  if (!lp->ptid.matches (*wait_ptid_p))
+	  if (!lp->ptid.matches (wait_ptid))
 	    {
 	      if (breakpoint_inserted_here_p (regcache->aspace (), pc))
 		leave_stopped = 1;
@@ -3579,7 +3587,11 @@ linux_nat_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus,
      meanwhile the event became uninteresting.  Don't bother resuming
      LWPs we're not going to wait for if they'd stop immediately.  */
   if (target_is_non_stop_p ())
-    iterate_over_lwps (minus_one_ptid, resume_stopped_resumed_lwps, &ptid);
+    iterate_over_lwps (minus_one_ptid,
+		       [=] (struct lwp_info *info)
+		       {
+			 return resume_stopped_resumed_lwps (info, ptid);
+		       });
 
   event_ptid = linux_nat_wait_1 (ptid, ourstatus, target_options);
 
@@ -3662,7 +3674,7 @@ kill_wait_one_lwp (pid_t pid)
 /* Callback for iterate_over_lwps.  */
 
 static int
-kill_callback (struct lwp_info *lp, void *data)
+kill_callback (struct lwp_info *lp)
 {
   kill_one_lwp (lp->ptid.lwp ());
   return 0;
@@ -3671,7 +3683,7 @@ kill_callback (struct lwp_info *lp, void *data)
 /* Callback for iterate_over_lwps.  */
 
 static int
-kill_wait_callback (struct lwp_info *lp, void *data)
+kill_wait_callback (struct lwp_info *lp)
 {
   kill_wait_one_lwp (lp->ptid.lwp ());
   return 0;
@@ -3720,16 +3732,16 @@ linux_nat_target::kill ()
 
       /* Stop all threads before killing them, since ptrace requires
 	 that the thread is stopped to sucessfully PTRACE_KILL.  */
-      iterate_over_lwps (ptid, stop_callback, NULL);
+      iterate_over_lwps (ptid, stop_callback);
       /* ... and wait until all of them have reported back that
 	 they're no longer running.  */
-      iterate_over_lwps (ptid, stop_wait_callback, NULL);
+      iterate_over_lwps (ptid, stop_wait_callback);
 
       /* Kill all LWP's ...  */
-      iterate_over_lwps (ptid, kill_callback, NULL);
+      iterate_over_lwps (ptid, kill_callback);
 
       /* ... and wait until we've flushed all events.  */
-      iterate_over_lwps (ptid, kill_wait_callback, NULL);
+      iterate_over_lwps (ptid, kill_wait_callback);
     }
 
   target_mourn_inferior (inferior_ptid);
@@ -4415,7 +4427,7 @@ linux_nat_target::async (int enable)
    event came out.  */
 
 static int
-linux_nat_stop_lwp (struct lwp_info *lwp, void *data)
+linux_nat_stop_lwp (struct lwp_info *lwp)
 {
   if (!lwp->stopped)
     {
@@ -4435,7 +4447,7 @@ linux_nat_stop_lwp (struct lwp_info *lwp, void *data)
 	  return 0;
 	}
 
-      stop_callback (lwp, NULL);
+      stop_callback (lwp);
       lwp->last_resume_kind = resume_stop;
     }
   else
@@ -4461,7 +4473,7 @@ linux_nat_stop_lwp (struct lwp_info *lwp, void *data)
 void
 linux_nat_target::stop (ptid_t ptid)
 {
-  iterate_over_lwps (ptid, linux_nat_stop_lwp, NULL);
+  iterate_over_lwps (ptid, linux_nat_stop_lwp);
 }
 
 void
diff --git a/gdb/nat/aarch64-linux-hw-point.c b/gdb/nat/aarch64-linux-hw-point.c
index eed0606..1efec9a 100644
--- a/gdb/nat/aarch64-linux-hw-point.c
+++ b/gdb/nat/aarch64-linux-hw-point.c
@@ -278,27 +278,17 @@ aarch64_align_watchpoint (CORE_ADDR addr, int len, CORE_ADDR *aligned_addr_p,
     *next_addr_orig_p = align_down (*next_addr_orig_p + alignment, alignment);
 }
 
-struct aarch64_dr_update_callback_param
-{
-  int is_watchpoint;
-  unsigned int idx;
-};
-
-/* Callback for iterate_over_lwps.  Records the
+/* Helper for aarch64_notify_debug_reg_change.  Records the
    information about the change of one hardware breakpoint/watchpoint
    setting for the thread LWP.
-   The information is passed in via PTR.
    N.B.  The actual updating of hardware debug registers is not
    carried out until the moment the thread is resumed.  */
 
 static int
-debug_reg_change_callback (struct lwp_info *lwp, void *ptr)
+debug_reg_change_callback (struct lwp_info *lwp, int is_watchpoint,
+			   unsigned int idx)
 {
-  struct aarch64_dr_update_callback_param *param_p
-    = (struct aarch64_dr_update_callback_param *) ptr;
   int tid = ptid_of_lwp (lwp).lwp ();
-  int idx = param_p->idx;
-  int is_watchpoint = param_p->is_watchpoint;
   struct arch_lwp_info *info = lwp_arch_private_info (lwp);
   dr_changed_t *dr_changed_ptr;
   dr_changed_t dr_changed;
@@ -356,13 +346,14 @@ static void
 aarch64_notify_debug_reg_change (const struct aarch64_debug_reg_state *state,
 				 int is_watchpoint, unsigned int idx)
 {
-  struct aarch64_dr_update_callback_param param;
   ptid_t pid_ptid = ptid_t (current_lwp_ptid ().pid ());
 
-  param.is_watchpoint = is_watchpoint;
-  param.idx = idx;
-
-  iterate_over_lwps (pid_ptid, debug_reg_change_callback, (void *) &param);
+  iterate_over_lwps (pid_ptid, [=] (struct lwp_info *info)
+			       {
+				 return debug_reg_change_callback (info,
+								   is_watchpoint,
+								   idx);
+			       });
 }
 
 /* Reconfigure STATE to be compatible with Linux kernels with the PR
diff --git a/gdb/nat/linux-nat.h b/gdb/nat/linux-nat.h
index 1e32dd9..29f43d8 100644
--- a/gdb/nat/linux-nat.h
+++ b/gdb/nat/linux-nat.h
@@ -20,6 +20,7 @@
 #ifndef NAT_LINUX_NAT_H
 #define NAT_LINUX_NAT_H
 
+#include "common/function-view.h"
 #include "target/waitstatus.h"
 
 struct lwp_info;
@@ -43,7 +44,7 @@ struct arch_lwp_info;
 extern ptid_t current_lwp_ptid (void);
 
 /* Function type for the CALLBACK argument of iterate_over_lwps.  */
-typedef int (iterate_over_lwps_ftype) (struct lwp_info *lwp, void *arg);
+typedef int (iterate_over_lwps_ftype) (struct lwp_info *lwp);
 
 /* Iterate over all LWPs.  Calls CALLBACK with its second argument set
    to DATA for every LWP in the list.  If CALLBACK returns nonzero for
@@ -51,9 +52,9 @@ typedef int (iterate_over_lwps_ftype) (struct lwp_info *lwp, void *arg);
    LWP immediately.  Otherwise return NULL.  This function must be
    provided by the client.  */
 
-extern struct lwp_info *iterate_over_lwps (ptid_t filter,
-					   iterate_over_lwps_ftype callback,
-					   void *data);
+extern struct lwp_info *iterate_over_lwps
+    (ptid_t filter,
+     gdb::function_view<iterate_over_lwps_ftype> callback);
 
 /* Return the ptid of LWP.  */
 
diff --git a/gdb/nat/x86-linux-dregs.c b/gdb/nat/x86-linux-dregs.c
index 33bbfa2..29b4ee1 100644
--- a/gdb/nat/x86-linux-dregs.c
+++ b/gdb/nat/x86-linux-dregs.c
@@ -76,7 +76,7 @@ x86_linux_dr_set (ptid_t ptid, int regnum, unsigned long value)
    the actual debug registers immediately prior to LWP resuming.  */
 
 static int
-update_debug_registers_callback (struct lwp_info *lwp, void *arg)
+update_debug_registers_callback (struct lwp_info *lwp)
 {
   lwp_set_debug_registers_changed (lwp, 1);
 
@@ -106,7 +106,7 @@ x86_linux_dr_set_addr (int regnum, CORE_ADDR addr)
 
   gdb_assert (DR_FIRSTADDR <= regnum && regnum <= DR_LASTADDR);
 
-  iterate_over_lwps (pid_ptid, update_debug_registers_callback, NULL);
+  iterate_over_lwps (pid_ptid, update_debug_registers_callback);
 }
 
 /* See nat/x86-linux-dregs.h.  */
@@ -124,7 +124,7 @@ x86_linux_dr_set_control (unsigned long control)
 {
   ptid_t pid_ptid = ptid_t (current_lwp_ptid ().pid ());
 
-  iterate_over_lwps (pid_ptid, update_debug_registers_callback, NULL);
+  iterate_over_lwps (pid_ptid, update_debug_registers_callback);
 }
 
 /* See nat/x86-linux-dregs.h.  */
diff --git a/gdb/s390-linux-nat.c b/gdb/s390-linux-nat.c
index 69a3df0..5f6c5be 100644
--- a/gdb/s390-linux-nat.c
+++ b/gdb/s390-linux-nat.c
@@ -833,7 +833,7 @@ s390_linux_nat_target::low_delete_thread (struct arch_lwp_info *arch_lwp)
 /* Iterator callback for s390_refresh_per_info.  */
 
 static int
-s390_refresh_per_info_cb (struct lwp_info *lp, void *arg)
+s390_refresh_per_info_cb (struct lwp_info *lp)
 {
   s390_mark_per_info_changed (lp);
 
@@ -849,7 +849,7 @@ s390_refresh_per_info (void)
 {
   ptid_t pid_ptid = ptid_t (current_lwp_ptid ().pid ());
 
-  iterate_over_lwps (pid_ptid, s390_refresh_per_info_cb, NULL);
+  iterate_over_lwps (pid_ptid, s390_refresh_per_info_cb);
   return 0;
 }