Simplify ui-out level code

Now that we use a vector to store the levels, we don't have to keep a
separate level field in ui_out to keep track of the current level.  We
can efficiently derive it from the vector size.  That causes a little
change in the meaning of the level, as in they are now 1-based instead
of 0-based (the initial level has the "id" 1 now), but it shouldn't
change anything in the behavior.

Additionally, push_level and pop_level don't really need to return the
new level, making them return void simplifies the code a bit.

Finally, the ui_out_begin/ui_out_end callbacks in the ui_out_impl
interface don't need to be passed the level, it's never actually used.

New in v2:

 - Remove or update stale comments.

gdb/ChangeLog:

	* ui-out.h (ui_out_begin_ftype): Remove level parameter.
	(ui_out_end_ftype): Likewise.
	* ui-out.c (struct ui_out) <level>: Replace field with a method
	that dynamically computes the result.
	(current_level): Get vector's back item instead of using
	uiout->level.
	(push_level): Make return type void.
	(pop_level): Make return type void and update access to
	ui_out::level.
	(uo_begin): Remove level parameter.
	(uo_end): Likewise.
	(ui_out_table_begin): Update access to uiout::level.
	(ui_out_begin): Don't read return value from push_level, call
	uiout->level() instead, update call to uo_begin.
	(ui_out_end): Don't read return value from pop_level, update
	call to uo_end.
	(verify_field): Update access to uiout->level.
	(ui_out_new): Don't initialize ui_out::level, call push_level
	to push the initial level instead of doing it by hand.
	* cli-out.c (cli_begin): Remove level parameter.
	(cli_end): Likewise.
	* mi/mi-out.c (mi_begin): Likewise.
	(mi_end): Likewise.

5 files changed, 60 insertions, 55 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index c45c5a2..8112edc 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,31 @@
 2016-12-01  Simon Marchi  <simon.marchi@polymtl.ca>
 
+	* ui-out.h (ui_out_begin_ftype): Remove level parameter.
+	(ui_out_end_ftype): Likewise.
+	* ui-out.c (struct ui_out) <level>: Replace field with a method
+	that dynamically computes the result.
+	(current_level): Get vector's back item instead of using
+	uiout->level.
+	(push_level): Make return type void.
+	(pop_level): Make return type void and update access to
+	ui_out::level.
+	(uo_begin): Remove level parameter.
+	(uo_end): Likewise.
+	(ui_out_table_begin): Update access to uiout::level.
+	(ui_out_begin): Don't read return value from push_level, call
+	uiout->level() instead, update call to uo_begin.
+	(ui_out_end): Don't read return value from pop_level, update
+	call to uo_end.
+	(verify_field): Update access to uiout->level.
+	(ui_out_new): Don't initialize ui_out::level, call push_level
+	to push the initial level instead of doing it by hand.
+	* cli-out.c (cli_begin): Remove level parameter.
+	(cli_end): Likewise.
+	* mi/mi-out.c (mi_begin): Likewise.
+	(mi_end): Likewise.
+
+2016-12-01  Simon Marchi  <simon.marchi@polymtl.ca>
+
 	* ui-out.c (struct ui_out_level): Replace with ...
 	(class ui_out_level): ... this.
 	(current_level): Update.
diff --git a/gdb/cli-out.c b/gdb/cli-out.c
index 4747f40..ac19e38 100644
--- a/gdb/cli-out.c
+++ b/gdb/cli-out.c
@@ -111,7 +111,6 @@ cli_table_header (struct ui_out *uiout, int width, enum ui_align alignment,
 static void
 cli_begin (struct ui_out *uiout,
 	   enum ui_out_type type,
-	   int level,
 	   const char *id)
 {
   cli_out_data *data = (cli_out_data *) ui_out_data (uiout);
@@ -124,8 +123,7 @@ cli_begin (struct ui_out *uiout,
 
 static void
 cli_end (struct ui_out *uiout,
-	 enum ui_out_type type,
-	 int level)
+	 enum ui_out_type type)
 {
   cli_out_data *data = (cli_out_data *) ui_out_data (uiout);
 
diff --git a/gdb/mi/mi-out.c b/gdb/mi/mi-out.c
index 9a2cb83..b6d25d3 100644
--- a/gdb/mi/mi-out.c
+++ b/gdb/mi/mi-out.c
@@ -45,8 +45,8 @@ static void mi_table_header (struct ui_out *uiout, int width,
 			     const std::string &col_name,
 			     const std::string &col_hdr);
 static void mi_begin (struct ui_out *uiout, enum ui_out_type type,
-		      int level, const char *id);
-static void mi_end (struct ui_out *uiout, enum ui_out_type type, int level);
+		      const char *id);
+static void mi_end (struct ui_out *uiout, enum ui_out_type type);
 static void mi_field_int (struct ui_out *uiout, int fldno, int width,
 			  enum ui_align alig, const char *fldname, int value);
 static void mi_field_skip (struct ui_out *uiout, int fldno, int width,
@@ -159,8 +159,7 @@ mi_table_header (struct ui_out *uiout, int width, enum ui_align alignment,
 /* Mark beginning of a list.  */
 
 void
-mi_begin (struct ui_out *uiout, enum ui_out_type type, int level,
-	  const char *id)
+mi_begin (struct ui_out *uiout, enum ui_out_type type, const char *id)
 {
   mi_out_data *data = (mi_out_data *) ui_out_data (uiout);
 
@@ -173,7 +172,7 @@ mi_begin (struct ui_out *uiout, enum ui_out_type type, int level,
 /* Mark end of a list.  */
 
 void
-mi_end (struct ui_out *uiout, enum ui_out_type type, int level)
+mi_end (struct ui_out *uiout, enum ui_out_type type)
 {
   mi_out_data *data = (mi_out_data *) ui_out_data (uiout);
 
diff --git a/gdb/ui-out.c b/gdb/ui-out.c
index 7d2411f..dc978a7 100644
--- a/gdb/ui-out.c
+++ b/gdb/ui-out.c
@@ -170,12 +170,14 @@ struct ui_out
     const struct ui_out_impl *impl;
     void *data;
 
-    /* Current level.  */
-    int level;
-
     /* Vector to store and track the ui-out levels.  */
     std::vector<std::unique_ptr<ui_out_level>> levels;
 
+    int level () const
+    {
+      return this->levels.size ();
+    }
+
     /* A table, if any.  At present only a single table is supported.  */
     struct ui_out_table table;
   };
@@ -184,36 +186,30 @@ struct ui_out
 static ui_out_level *
 current_level (struct ui_out *uiout)
 {
-  return uiout->levels[uiout->level].get ();
+  return uiout->levels.back ().get ();
 }
 
-/* Create a new level, of TYPE.  Return the new level's index.  */
-static int
+/* Create a new level, of TYPE.  */
+static void
 push_level (struct ui_out *uiout,
 	    enum ui_out_type type)
 {
   std::unique_ptr<ui_out_level> level (new ui_out_level (type));
 
   uiout->levels.push_back (std::move (level));
-  uiout->level++;
-
-  return uiout->level;
 }
 
-/* Discard the current level, return the discarded level's index.
-   TYPE is the type of the level being discarded.  */
-static int
+/* Discard the current level.  TYPE is the type of the level being
+   discarded.  */
+static void
 pop_level (struct ui_out *uiout,
 	   enum ui_out_type type)
 {
   /* We had better not underflow the buffer.  */
-  gdb_assert (uiout->level > 0);
+  gdb_assert (uiout->level () > 0);
   gdb_assert (current_level (uiout)->type () == type);
 
   uiout->levels.pop_back ();
-  uiout->level--;
-
-  return uiout->level + 1;
 }
 
 /* These are the interfaces to implementation functions.  */
@@ -228,10 +224,9 @@ static void uo_table_header (struct ui_out *uiout, int width,
 			     const std::string &col_hdr);
 static void uo_begin (struct ui_out *uiout,
 		      enum ui_out_type type,
-		      int level, const char *id);
+		      const char *id);
 static void uo_end (struct ui_out *uiout,
-		    enum ui_out_type type,
-		    int level);
+		    enum ui_out_type type);
 static void uo_field_int (struct ui_out *uiout, int fldno, int width,
 			  enum ui_align align, const char *fldname, int value);
 static void uo_field_skip (struct ui_out *uiout, int fldno, int width,
@@ -277,7 +272,7 @@ previous table_end."));
 
   uiout->table.flag = 1;
   uiout->table.body_flag = 0;
-  uiout->table.entry_level = uiout->level + 1;
+  uiout->table.entry_level = uiout->level () + 1;
   uiout->table.columns = nbrofcols;
   uiout->table.id = tblid;
 
@@ -357,8 +352,6 @@ ui_out_begin (struct ui_out *uiout,
 	      enum ui_out_type type,
 	      const char *id)
 {
-  int new_level;
-
   if (uiout->table.flag && !uiout->table.body_flag)
     internal_error (__FILE__, __LINE__,
 		    _("table header or table_body expected; lists must be \
@@ -379,24 +372,24 @@ specified after table_body."));
     verify_field (uiout, &fldno, &width, &align);
   }
 
-  new_level = push_level (uiout, type);
+  push_level (uiout, type);
 
   /* If the push puts us at the same level as a table row entry, we've
      got a new table row.  Put the header pointer back to the start.  */
   if (uiout->table.body_flag
-      && uiout->table.entry_level == new_level)
+      && uiout->table.entry_level == uiout->level ())
     uiout->table.headers_iterator = uiout->table.headers.begin ();
 
-  uo_begin (uiout, type, new_level, id);
+  uo_begin (uiout, type, id);
 }
 
 void
 ui_out_end (struct ui_out *uiout,
 	    enum ui_out_type type)
 {
-  int old_level = pop_level (uiout, type);
+  pop_level (uiout, type);
 
-  uo_end (uiout, type, old_level);
+  uo_end (uiout, type);
 }
 
 struct ui_out_end_cleanup_data
@@ -652,22 +645,20 @@ clear_table (struct ui_out *uiout)
 void
 uo_begin (struct ui_out *uiout,
 	  enum ui_out_type type,
-	  int level,
 	  const char *id)
 {
   if (uiout->impl->begin == NULL)
     return;
-  uiout->impl->begin (uiout, type, level, id);
+  uiout->impl->begin (uiout, type, id);
 }
 
 void
 uo_end (struct ui_out *uiout,
-	enum ui_out_type type,
-	int level)
+	enum ui_out_type type)
 {
   if (uiout->impl->end == NULL)
     return;
-  uiout->impl->end (uiout, type, level);
+  uiout->impl->end (uiout, type);
 }
 
 void
@@ -832,17 +823,12 @@ verify_field (struct ui_out *uiout, int *fldno, int *width,
 	internal_error (__FILE__, __LINE__,
 			_("table_body missing; table fields must be \
 specified after table_body and inside a list."));
-      /* NOTE: cagney/2001-12-08: There was a check here to ensure
-	 that this code was only executed when uiout->level was
-	 greater than zero.  That no longer applies - this code is run
-	 before each table row tuple is started and at that point the
-	 level is zero.  */
     }
 
   current->inc_field_count ();
 
   if (uiout->table.body_flag
-      && uiout->table.entry_level == uiout->level
+      && uiout->table.entry_level == uiout->level ()
       && get_next_header (uiout, fldno, width, align, &text))
     {
       if (*fldno != current->field_count ())
@@ -906,11 +892,9 @@ ui_out_new (const struct ui_out_impl *impl, void *data,
   uiout->flags = flags;
   uiout->table.flag = 0;
   uiout->table.body_flag = 0;
-  uiout->level = 0;
 
-  /* Create uiout->level 0, the default level.  */
-  std::unique_ptr<ui_out_level> level (new ui_out_level (ui_out_type_tuple));
-  uiout->levels.push_back (std::move (level));
+  /* Create the ui-out level #1, the default level.  */
+  push_level (uiout, ui_out_type_tuple);
 
   uiout->table.headers_iterator = uiout->table.headers.end ();
 
diff --git a/gdb/ui-out.h b/gdb/ui-out.h
index ed2911d..06c05e2 100644
--- a/gdb/ui-out.h
+++ b/gdb/ui-out.h
@@ -157,14 +157,12 @@ typedef void (table_header_ftype) (struct ui_out * uiout, int width,
 				   enum ui_align align,
 				   const std::string &col_name,
 				   const std::string &col_hdr);
-/* Note: level 0 is the top-level so LEVEL is always greater than
-   zero.  */
+
 typedef void (ui_out_begin_ftype) (struct ui_out *uiout,
 				   enum ui_out_type type,
-				   int level, const char *id);
+				   const char *id);
 typedef void (ui_out_end_ftype) (struct ui_out *uiout,
-				 enum ui_out_type type,
-				 int level);
+				 enum ui_out_type type);
 typedef void (field_int_ftype) (struct ui_out * uiout, int fldno, int width,
 				enum ui_align align,
 				const char *fldname, int value);