Some get_last_target_status tweaks

- 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.

gdb/ChangeLog

@@ -1,3 +1,27 @@
+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.
+
 2020-01-10  Pedro Alves  <palves@redhat.com>
 
 	* gdbthread.h (scoped_restore_current_thread)

gdb/break-catch-sig.c

@@ -181,12 +181,11 @@ static enum print_stop_action
 signal_catchpoint_print_it (bpstat bs)
 {
   struct breakpoint *b = bs->breakpoint_at;
-  ptid_t ptid;
   struct target_waitstatus last;
   const char *signal_name;
   struct ui_out *uiout = current_uiout;
 
-  get_last_target_status (&ptid, &last);
+  get_last_target_status (nullptr, &last);
 
   signal_name = signal_to_name_or_int (last.value.sig);
 

gdb/break-catch-syscall.c

@@ -182,12 +182,11 @@ print_it_catch_syscall (bpstat bs)
      syscall is.  It can be in the TARGET_WAITKIND_SYSCALL_ENTRY
      or TARGET_WAITKIND_SYSCALL_RETURN, and depending on it we
      must print "called syscall" or "returned from syscall".  */
-  ptid_t ptid;
   struct target_waitstatus last;
   struct syscall s;
   struct gdbarch *gdbarch = bs->bp_location_at->gdbarch;
 
-  get_last_target_status (&ptid, &last);
+  get_last_target_status (nullptr, &last);
 
   get_syscall_by_number (gdbarch, last.value.syscall_number, &s);
 

gdb/infcmd.c

@@ -851,9 +851,8 @@ continue_command (const char *args, int from_tty)
       else
 	{
 	  ptid_t last_ptid;
-	  struct target_waitstatus ws;
 
-	  get_last_target_status (&last_ptid, &ws);
+	  get_last_target_status (&last_ptid, nullptr);
 	  tp = find_thread_ptid (last_ptid);
 	}
       if (tp != NULL)
@@ -1993,11 +1992,7 @@ info_program_command (const char *args, int from_tty)
   if (non_stop)
     ptid = inferior_ptid;
   else
-    {
+    get_last_target_status (&ptid, nullptr);
-      struct target_waitstatus ws;
-
-      get_last_target_status (&ptid, &ws);
-    }
 
   if (ptid == null_ptid || ptid == minus_one_ptid)
     error (_("No selected thread."));

gdb/infrun.c

@@ -78,8 +78,6 @@ static void follow_inferior_reset_breakpoints (void);
 
 static int currently_stepping (struct thread_info *tp);
 
-void nullify_last_target_wait_ptid (void);
-
 static void insert_hp_step_resume_breakpoint_at_frame (struct frame_info *);
 
 static void insert_step_resume_breakpoint_at_caller (struct frame_info *);
@@ -3103,7 +3101,7 @@ init_wait_for_inferior (void)
 
   clear_proceed_status (0);
 
-  target_last_wait_ptid = minus_one_ptid;
+  nullify_last_target_wait_ptid ();
 
   previous_inferior_ptid = inferior_ptid;
 }
@@ -3847,7 +3845,7 @@ init_thread_stepping_state (struct thread_info *tss)
   tss->step_after_step_resume_breakpoint = 0;
 }
 
-/* Set the cached copy of the last ptid/waitstatus.  */
+/* See infrun.h.  */
 
 void
 set_last_target_status (ptid_t ptid, struct target_waitstatus status)
@@ -3856,22 +3854,24 @@ set_last_target_status (ptid_t ptid, struct target_waitstatus status)
   target_last_waitstatus = status;
 }
 
-/* Return the cached copy of the last pid/waitstatus returned by
+/* See infrun.h.  */
-   target_wait()/deprecated_target_wait_hook().  The data is actually
-   cached by handle_inferior_event(), which gets called immediately
-   after target_wait()/deprecated_target_wait_hook().  */
 
 void
-get_last_target_status (ptid_t *ptidp, struct target_waitstatus *status)
+get_last_target_status (ptid_t *ptid, struct target_waitstatus *status)
 {
-  *ptidp = target_last_wait_ptid;
+  if (ptid != nullptr)
+    *ptid = target_last_wait_ptid;
+  if (status != nullptr)
     *status = target_last_waitstatus;
 }
 
+/* See infrun.h.  */
+
 void
 nullify_last_target_wait_ptid (void)
 {
   target_last_wait_ptid = minus_one_ptid;
+  target_last_waitstatus = {};
 }
 
 /* Switch thread contexts.  */
@@ -7876,10 +7876,9 @@ void
 print_stop_event (struct ui_out *uiout, bool displays)
 {
   struct target_waitstatus last;
-  ptid_t last_ptid;
   struct thread_info *tp;
 
-  get_last_target_status (&last_ptid, &last);
+  get_last_target_status (nullptr, &last);
 
   {
     scoped_restore save_uiout = make_scoped_restore (&current_uiout, uiout);
@@ -7998,9 +7997,8 @@ int
 normal_stop (void)
 {
   struct target_waitstatus last;
-  ptid_t last_ptid;
 
-  get_last_target_status (&last_ptid, &last);
+  get_last_target_status (nullptr, &last);
 
   new_stop_id ();
 

gdb/infrun.h

@@ -101,12 +101,21 @@ extern void wait_for_inferior (void);
    target, false otherwise.  */
 extern int normal_stop (void);
 
+/* Return the cached copy of the last ptid/waitstatus returned
+   by target_wait()/deprecated_target_wait_hook().  The data is
+   actually cached by handle_inferior_event(), which gets called
+   immediately after target_wait()/deprecated_target_wait_hook().  */
 extern void get_last_target_status (ptid_t *ptid,
 				    struct target_waitstatus *status);
 
+/* Set the cached copy of the last ptid/waitstatus.  */
 extern void set_last_target_status (ptid_t ptid,
 				    struct target_waitstatus status);
 
+/* Clear the cached copy of the last ptid/waitstatus returned by
+   target_wait().  */
+extern void nullify_last_target_wait_ptid ();
+
 /* Stop all threads.  Only returns after everything is halted.  */
 extern void stop_all_threads (void);
 

gdb/linux-fork.c

@@ -215,7 +215,6 @@ call_lseek (int fd, off_t offset, int whence)
 static void
 fork_load_infrun_state (struct fork_info *fp)
 {
-  extern void nullify_last_target_wait_ptid ();
   int i;
 
   linux_nat_switch_fork (fp->ptid);

gdb/linux-nat.c

@@ -1315,10 +1315,9 @@ get_detach_signal (struct lwp_info *lp)
 	}
       else if (!target_is_non_stop_p ())
 	{
-	  struct target_waitstatus last;
 	  ptid_t last_ptid;
 
-	  get_last_target_status (&last_ptid, &last);
+	  get_last_target_status (&last_ptid, nullptr);
 
 	  if (lp->ptid.lwp () == last_ptid.lwp ())
 	    signo = tp->suspend.stop_signal;