gdb: Add a class to track last display symtab and line information

In stack.c we currently have a set of static global variables to track
the last displayed symtab and line.  This commit moves all of these
into a class and adds an instance of the class to track the same
information.

The API into stack.c is unchanged after this cleanup.

There should be no user visible changes after this commit.

gdb/ChangeLog:

	* stack.c (set_last_displayed_sal): Delete.
	(last_displayed_sal_valid): Delete.
	(last_displayed_pspace): Delete.
	(last_displayed_addr): Delete.
	(last_displayed_symtab): Delete.
	(last_displayed_line): Delete.
	(class last_displayed_symtab_info_type): New.
	(last_displayed_symtab_info): New static global variable.
	(print_frame_info): Call methods on last_displayed_symtab_info.
	(clear_last_displayed_sal): Update header comment, and make use of
	last_displayed_symtab_info.
	(last_displayed_sal_is_valid): Likewise.
	(get_last_displayed_pspace): Likewise.
	(get_last_displayed_addr): Likewise.
	(get_last_displayed_symtab): Likewise.
	(get_last_displayed_line): Likewise.
	(get_last_displayed_sal): Likewise.
	* stack.h (clear_last_displayed_sal): Update header comment.
	(last_displayed_sal_is_valid): Likewise.
	(get_last_displayed_pspace): Likewise.
	(get_last_displayed_addr): Likewise.
	(get_last_displayed_symtab): Likewise.
	(get_last_displayed_line): Likewise.
	(get_last_displayed_sal): Likewise.

Change-Id: Ia3dbfe267feec03108c5c8ed8bd94fc0a030c3ed

1 files changed, 27 insertions, 3 deletions

diff --git a/gdb/stack.h b/gdb/stack.h
index 28d2273..9b038f0 100644
--- a/gdb/stack.h
+++ b/gdb/stack.h
@@ -54,14 +54,38 @@ void get_user_print_what_frame_info (gdb::optional<enum print_what> *what);
 
 bool frame_show_address (struct frame_info *frame, struct symtab_and_line sal);
 
-/* Get or set the last displayed symtab and line, which is, e.g. where we set a
- * breakpoint when `break' is supplied with no arguments.  */
+/* Forget the last sal we displayed.  */
+
 void clear_last_displayed_sal (void);
-int last_displayed_sal_is_valid (void);
+
+/* Is our record of the last sal we displayed valid?  If not, the
+   get_last_displayed_* functions will return NULL or 0, as appropriate.  */
+
+bool last_displayed_sal_is_valid (void);
+
+/* Get the pspace of the last sal we displayed, if it's valid, otherwise
+   return nullptr.  */
+
 struct program_space* get_last_displayed_pspace (void);
+
+/* Get the address of the last sal we displayed, if it's valid, otherwise
+   return an address of 0.  */
+
 CORE_ADDR get_last_displayed_addr (void);
+
+/* Get the symtab of the last sal we displayed, if it's valid, otherwise
+   return nullptr.  */
+
 struct symtab* get_last_displayed_symtab (void);
+
+/* Get the line of the last sal we displayed, if it's valid, otherwise
+   return 0.  */
+
 int get_last_displayed_line (void);
+
+/* Get the last sal we displayed, if it's valid, otherwise return a
+   symtab_and_line constructed in its default state.  */
+
 symtab_and_line get_last_displayed_sal ();
 
 /* Completer for the "frame apply all" command.  */