Make target_ops::has_execution take an 'inferior *' instead of a ptid_t

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.

gdb/ChangeLog

@@ -1,3 +1,31 @@
+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.
+
 2020-01-10  Pedro Alves  <palves@redhat.com>
 
 	* exceptions.c (print_flush): Remove current_top_target() check.

gdb/corelow.c

@@ -94,7 +94,7 @@ public:
   bool has_memory () override;
   bool has_stack () override;
   bool has_registers () override;
-  bool has_execution (ptid_t) override { return false; }
+  bool has_execution (inferior *inf) override { return false; }
 
   bool info_proc (const char *, enum info_proc_what) override;
 

gdb/inferior.c

@@ -345,7 +345,7 @@ number_of_live_inferiors (void)
   int num_inf = 0;
 
   for (inferior *inf : all_non_exited_inferiors ())
-    if (target_has_execution_1 (ptid_t (inf->pid)))
+    if (inf->has_execution ())
       for (thread_info *tp ATTRIBUTE_UNUSED : inf->non_exited_threads ())
 	{
 	  /* Found a live thread in this inferior, go to the next

gdb/inferior.h

@@ -339,6 +339,9 @@ public:
   /* Returns true if we can delete this inferior.  */
   bool deletable () const { return refcount () == 0; }
 
+  bool has_execution ()
+  { return target_has_execution_1 (this); }
+
   /* Pointer to next inferior in singly-linked list of inferiors.  */
   struct inferior *next = NULL;
 

gdb/linux-thread-db.c

@@ -1622,7 +1622,7 @@ thread_db_target::update_thread_list ()
 	 stop.  That uses thread_db entry points that do not walk
 	 libpthread's thread list, so should be safe, as well as more
 	 efficient.  */
-      if (target_has_execution_1 (thread->ptid))
+      if (thread->inf->has_execution ())
 	continue;
 
       thread_db_find_new_threads_1 (thread);

gdb/process-stratum-target.c

@@ -77,9 +77,9 @@ process_stratum_target::has_registers ()
 }
 
 bool
-process_stratum_target::has_execution (ptid_t the_ptid)
+process_stratum_target::has_execution (inferior *inf)
 {
-  /* If there's no thread selected, then we can't make it run through
-     hoops.  */
-  return the_ptid != null_ptid;
+  /* If there's a process running already, we can't make it run
+     through hoops.  */
+  return inf->pid != 0;
 }

gdb/process-stratum-target.h

@@ -50,7 +50,7 @@ public:
   bool has_memory () override;
   bool has_stack () override;
   bool has_registers () override;
-  bool has_execution (ptid_t the_ptid) override;
+  bool has_execution (inferior *inf) override;
 };
 
 #endif /* !defined (PROCESS_STRATUM_TARGET_H) */

gdb/record-full.c

@@ -319,7 +319,7 @@ public:
 			 struct bp_target_info *,
 			 enum remove_bp_reason) override;
 
-  bool has_execution (ptid_t) override;
+  bool has_execution (inferior *inf) override;
 };
 
 static record_full_target record_full_ops;
@@ -2244,7 +2244,7 @@ record_full_core_target::remove_breakpoint (struct gdbarch *gdbarch,
 /* "has_execution" method for prec over corefile.  */
 
 bool
-record_full_core_target::has_execution (ptid_t the_ptid)
+record_full_core_target::has_execution (inferior *inf)
 {
   return true;
 }

gdb/target.c

@@ -223,20 +223,20 @@ target_has_registers_1 (void)
   return 0;
 }
 
-int
-target_has_execution_1 (ptid_t the_ptid)
+bool
+target_has_execution_1 (inferior *inf)
 {
   for (target_ops *t = current_top_target (); t != NULL; t = t->beneath ())
-    if (t->has_execution (the_ptid))
-      return 1;
+    if (t->has_execution (inf))
+      return true;
 
-  return 0;
+  return false;
 }
 
 int
 target_has_execution_current (void)
 {
-  return target_has_execution_1 (inferior_ptid);
+  return target_has_execution_1 (current_inferior ());
 }
 
 /* This is used to implement the various target commands.  */

gdb/target.h

@@ -686,7 +686,7 @@ struct target_ops
     virtual bool has_memory () { return false; }
     virtual bool has_stack () { return false; }
     virtual bool has_registers () { return false; }
-    virtual bool has_execution (ptid_t) { return false; }
+    virtual bool has_execution (inferior *inf) { return false; }
 
     /* Control thread execution.  */
     virtual thread_control_capabilities get_thread_control_capabilities ()
@@ -1790,9 +1790,10 @@ extern int target_has_registers_1 (void);
    case this will become true after to_create_inferior or
    to_attach.  */
 
-extern int target_has_execution_1 (ptid_t);
+extern bool target_has_execution_1 (inferior *inf);
 
-/* Like target_has_execution_1, but always passes inferior_ptid.  */
+/* Like target_has_execution_1, but always passes
+   current_inferior().  */
 
 extern int target_has_execution_current (void);
 

gdb/tracefile.h

@@ -127,7 +127,7 @@ public:
   bool has_memory () override;
   bool has_stack () override;
   bool has_registers () override;
-  bool has_execution (ptid_t) override { return false; }
+  bool has_execution (inferior *inf) override { return false; }
   bool thread_alive (ptid_t ptid) override;
 };