Add observable to watch current source symtab

This patch adds an observable, so that a later patch can change the
TUI to notice when the user has selected a new source symtab, say via
"list".

gdb/ChangeLog
2019-12-20  Tom Tromey  <tom@tromey.com>

	* source.c (struct current_source_location) <set, symtab, line>:
	New methods.
	<m_symtab, m_line>: Rename.  Now private.
	(get_current_source_symtab_and_line)
	(set_default_source_symtab_and_line)
	(set_current_source_symtab_and_line)
	(clear_current_source_symtab_and_line, select_source_symtab)
	(info_source_command, print_source_lines_base)
	(info_line_command, search_command_helper): Update.
	* observable.h (current_source_symtab_and_line_changed): Declare
	observable.
	* observable.c (current_source_symtab_and_line_changed): Define
	observable.

Change-Id: I3c0f6b40f2df84b590bdf5b5ec5ccd8423bb7f22

4 files changed, 89 insertions, 37 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f910703..3939eba 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,21 @@
 2019-12-20  Tom Tromey  <tom@tromey.com>
 
+	* source.c (struct current_source_location) <set, symtab, line>:
+	New methods.
+	<m_symtab, m_line>: Rename.  Now private.
+	(get_current_source_symtab_and_line)
+	(set_default_source_symtab_and_line)
+	(set_current_source_symtab_and_line)
+	(clear_current_source_symtab_and_line, select_source_symtab)
+	(info_source_command, print_source_lines_base)
+	(info_line_command, search_command_helper): Update.
+	* observable.h (current_source_symtab_and_line_changed): Declare
+	observable.
+	* observable.c (current_source_symtab_and_line_changed): Define
+	observable.
+
+2019-12-20  Tom Tromey  <tom@tromey.com>
+
 	* tui/tui-hooks.c (tui_before_prompt): Change parameter to bool.
 	(tui_before_prompt, tui_normal_stop): Update.
 
diff --git a/gdb/observable.c b/gdb/observable.c
index c077b02..4806e10 100644
--- a/gdb/observable.c
+++ b/gdb/observable.c
@@ -75,6 +75,7 @@ DEFINE_OBSERVABLE (inferior_call_post);
 DEFINE_OBSERVABLE (register_changed);
 DEFINE_OBSERVABLE (user_selected_context_changed);
 DEFINE_OBSERVABLE (source_styling_changed);
+DEFINE_OBSERVABLE (current_source_symtab_and_line_changed);
 
 } /* namespace observers */
 } /* namespace gdb */
diff --git a/gdb/observable.h b/gdb/observable.h
index 9ce0099..0c41aa3 100644
--- a/gdb/observable.h
+++ b/gdb/observable.h
@@ -241,6 +241,12 @@ extern observable<user_selected_what /* selection */>
    should be reconsulted.  */
 extern observable<> source_styling_changed;
 
+/* The CLI's notion of the current source has changed.  This differs
+   from user_selected_context_changed in that it is also set by the
+   "list" command.  */
+
+extern observable<> current_source_symtab_and_line_changed;
+
 } /* namespace observers */
 
 } /* namespace gdb */
diff --git a/gdb/source.c b/gdb/source.c
index cf752a6..f5cd2a3 100644
--- a/gdb/source.c
+++ b/gdb/source.c
@@ -47,6 +47,7 @@
 #include "gdbsupport/pathstuff.h"
 #include "source-cache.h"
 #include "cli/cli-style.h"
+#include "observable.h"
 
 #define OPEN_MODE (O_RDONLY | O_BINARY)
 #define FDOPEN_MODE FOPEN_RB
@@ -71,13 +72,39 @@ static struct substitute_path_rule *substitute_path_rules = NULL;
 
 struct current_source_location
 {
+public:
+
+  current_source_location () = default;
+
+  /* Set the value.  */
+  void set (struct symtab *s, int l)
+  {
+    m_symtab = s;
+    m_line = l;
+    gdb::observers::current_source_symtab_and_line_changed.notify ();
+  }
+
+  /* Get the symtab.  */
+  struct symtab *symtab () const
+  {
+    return m_symtab;
+  }
+
+  /* Get the line number.  */
+  int line () const
+  {
+    return m_line;
+  }
+
+private:
+
   /* Symtab of default file for listing lines of.  */
 
-  struct symtab *symtab = nullptr;
+  struct symtab *m_symtab = nullptr;
 
   /* Default next line to list.  */
 
-  int line = 0;
+  int m_line = 0;
 };
 
 static program_space_key<current_source_location> current_source_key;
@@ -191,8 +218,8 @@ get_current_source_symtab_and_line (void)
   current_source_location *loc = get_source_location (current_program_space);
 
   cursal.pspace = current_program_space;
-  cursal.symtab = loc->symtab;
-  cursal.line = loc->line;
+  cursal.symtab = loc->symtab ();
+  cursal.line = loc->line ();
   cursal.pc = 0;
   cursal.end = 0;
   
@@ -215,7 +242,7 @@ set_default_source_symtab_and_line (void)
 
   /* Pull in a current source symtab if necessary.  */
   current_source_location *loc = get_source_location (current_program_space);
-  if (loc->symtab == nullptr)
+  if (loc->symtab () == nullptr)
     select_source_symtab (0);
 }
 
@@ -232,13 +259,12 @@ set_current_source_symtab_and_line (const symtab_and_line &sal)
   current_source_location *loc = get_source_location (sal.pspace);
 
   cursal.pspace = sal.pspace;
-  cursal.symtab = loc->symtab;
-  cursal.line = loc->line;
+  cursal.symtab = loc->symtab ();
+  cursal.line = loc->line ();
   cursal.pc = 0;
   cursal.end = 0;
 
-  loc->symtab = sal.symtab;
-  loc->line = sal.line;
+  loc->set (sal.symtab, sal.line);
 
   /* Force the next "list" to center around the current line.  */
   clear_lines_listed_range ();
@@ -252,8 +278,7 @@ void
 clear_current_source_symtab_and_line (void)
 {
   current_source_location *loc = get_source_location (current_program_space);
-  loc->symtab = nullptr;
-  loc->line = 0;
+  loc->set (nullptr, 0);
 }
 
 /* See source.h.  */
@@ -265,13 +290,12 @@ select_source_symtab (struct symtab *s)
     {
       current_source_location *loc
 	= get_source_location (SYMTAB_PSPACE (s));
-      loc->symtab = s;
-      loc->line = 1;
+      loc->set (s, 1);
       return;
     }
 
   current_source_location *loc = get_source_location (current_program_space);
-  if (loc->symtab != nullptr)
+  if (loc->symtab () != nullptr)
     return;
 
   /* Make the default place to list be the function `main'
@@ -280,15 +304,14 @@ select_source_symtab (struct symtab *s)
   if (bsym.symbol != nullptr && SYMBOL_CLASS (bsym.symbol) == LOC_BLOCK)
     {
       symtab_and_line sal = find_function_start_sal (bsym.symbol, true);
-      loc->symtab = sal.symtab;
-      loc->line = std::max (sal.line - (lines_to_list - 1), 1);
+      loc->set (sal.symtab, std::max (sal.line - (lines_to_list - 1), 1));
       return;
     }
 
   /* Alright; find the last file in the symtab list (ignoring .h's
      and namespace symtabs).  */
 
-  loc->line = 1;
+  struct symtab *new_symtab = nullptr;
 
   for (objfile *ofp : current_program_space->objfiles ())
     {
@@ -301,12 +324,13 @@ select_source_symtab (struct symtab *s)
 
 	      if (!(len > 2 && (strcmp (&name[len - 2], ".h") == 0
 				|| strcmp (name, "<<C++-namespaces>>") == 0)))
-		loc->symtab = symtab;
+		new_symtab = symtab;
 	    }
 	}
     }
 
-  if (loc->symtab != nullptr)
+  loc->set (new_symtab, 1);
+  if (new_symtab != nullptr)
     return;
 
   for (objfile *objfile : current_program_space->objfiles ())
@@ -314,10 +338,13 @@ select_source_symtab (struct symtab *s)
       if (objfile->sf)
 	s = objfile->sf->qf->find_last_source_symtab (objfile);
       if (s)
-	loc->symtab = s;
+	new_symtab = s;
+    }
+  if (new_symtab != nullptr)
+    {
+      loc->set (new_symtab,1);
+      return;
     }
-  if (loc->symtab != nullptr)
-    return;
 
   error (_("Can't find a default source file"));
 }
@@ -641,7 +668,7 @@ info_source_command (const char *ignore, int from_tty)
 {
   current_source_location *loc
     = get_source_location (current_program_space);
-  struct symtab *s = loc->symtab;
+  struct symtab *s = loc->symtab ();
   struct compunit_symtab *cust;
 
   if (!s)
@@ -1203,8 +1230,7 @@ print_source_lines_base (struct symtab *s, int line, int stopline,
   current_source_location *loc
     = get_source_location (current_program_space);
 
-  loc->symtab = s;
-  loc->line = line;
+  loc->set (s, line);
   first_line_listed = line;
 
   /* If printing of source lines is disabled, just print file and line
@@ -1294,17 +1320,18 @@ print_source_lines_base (struct symtab *s, int line, int stopline,
     }
 
   const char *iter = lines.c_str ();
+  int new_lineno = loc->line ();
   while (nlines-- > 0 && *iter != '\0')
     {
       char buf[20];
 
-      last_line_listed = loc->line;
+      last_line_listed = loc->line ();
       if (flags & PRINT_SOURCE_LINES_FILENAME)
         {
           uiout->text (symtab_to_filename_for_display (s));
           uiout->text (":");
         }
-      xsnprintf (buf, sizeof (buf), "%d\t", loc->line++);
+      xsnprintf (buf, sizeof (buf), "%d\t", new_lineno++);
       uiout->text (buf);
 
       while (*iter != '\0')
@@ -1359,6 +1386,8 @@ print_source_lines_base (struct symtab *s, int line, int stopline,
 	}
       uiout->text ("\n");
     }
+
+  loc->set (loc->symtab (), new_lineno);
 }
 
 
@@ -1398,12 +1427,12 @@ info_line_command (const char *arg, int from_tty)
     {
       current_source_location *loc
 	= get_source_location (current_program_space);
-      curr_sal.symtab = loc->symtab;
+      curr_sal.symtab = loc->symtab ();
       curr_sal.pspace = current_program_space;
       if (last_line_listed != 0)
 	curr_sal.line = last_line_listed;
       else
-	curr_sal.line = loc->line;
+	curr_sal.line = loc->line ();
 
       sals = curr_sal;
     }
@@ -1507,12 +1536,12 @@ search_command_helper (const char *regex, int from_tty, bool forward)
 
   current_source_location *loc
     = get_source_location (current_program_space);
-  if (loc->symtab == nullptr)
+  if (loc->symtab () == nullptr)
     select_source_symtab (0);
 
-  scoped_fd desc (open_source_file (loc->symtab));
+  scoped_fd desc (open_source_file (loc->symtab ()));
   if (desc.get () < 0)
-    perror_with_name (symtab_to_filename_for_display (loc->symtab));
+    perror_with_name (symtab_to_filename_for_display (loc->symtab ()));
 
   int line = (forward
 	      ? last_line_listed + 1
@@ -1520,12 +1549,12 @@ search_command_helper (const char *regex, int from_tty, bool forward)
 
   const std::vector<off_t> *offsets;
   if (line < 1
-      || !g_source_cache.get_line_charpos (loc->symtab, &offsets)
+      || !g_source_cache.get_line_charpos (loc->symtab (), &offsets)
       || line > offsets->size ())
     error (_("Expression not found"));
 
   if (lseek (desc.get (), (*offsets)[line - 1], 0) < 0)
-    perror_with_name (symtab_to_filename_for_display (loc->symtab));
+    perror_with_name (symtab_to_filename_for_display (loc->symtab ()));
 
   gdb_file_up stream = desc.to_file (FDOPEN_MODE);
   clearerr (stream.get ());
@@ -1560,9 +1589,9 @@ search_command_helper (const char *regex, int from_tty, bool forward)
       if (re_exec (buf.data ()) > 0)
 	{
 	  /* Match!  */
-	  print_source_lines (loc->symtab, line, line + 1, 0);
+	  print_source_lines (loc->symtab (), line, line + 1, 0);
 	  set_internalvar_integer (lookup_internalvar ("_"), line);
-	  loc->line = std::max (line - lines_to_list / 2, 1);
+	  loc->set (loc->symtab (), std::max (line - lines_to_list / 2, 1));
 	  return;
 	}
 
@@ -1576,7 +1605,7 @@ search_command_helper (const char *regex, int from_tty, bool forward)
 	  if (fseek (stream.get (), (*offsets)[line - 1], 0) < 0)
 	    {
 	      const char *filename
-		= symtab_to_filename_for_display (loc->symtab);
+		= symtab_to_filename_for_display (loc->symtab ());
 	      perror_with_name (filename);
 	    }
 	}