gdb: Change "list ." command's error when no debuginfo is available

Currently, when a user tries to list the current location, there are 2
different error messages that can happen, either:

    (gdb) list .
    No symbol table is loaded.  Use the "file" command.
or
    (gdb) list .
    No debug information available to print source lines.

The difference here is if gdb can find any symtabs at all or not, which
is not something too important for end-users - and isn't informative at
all. This commit changes it so that the error always says that there
isn't debug information available, with these two variants:

    (gdb) list .
    Insufficient debug info for showing source lines at current PC (0x55555555511d).
or
    (gdb) list .
    Insufficient debug info for showing source lines at default location.

The difference now is if the inferior has started already, which is
controlled by the user and may be useful.

Unfortunately, it isn't as easy to differentiate if the symtab found for
other list parameters is correct, so other invocations, such as "list +"
still retain their original error message.

Co-Authored-By: Simon Marchi <simark@simark.ca>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Andrew Burgess <aburgess@redhat.com>

1 files changed, 30 insertions, 11 deletions

diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index 476138a..5d49e39 100644
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -1234,37 +1234,39 @@ list_command (const char *arg, int from_tty)
   /* Pull in the current default source line if necessary.  */
   if (arg == NULL || ((arg[0] == '+' || arg[0] == '-' || arg[0] == '.') && arg[1] == '\0'))
     {
-      set_default_source_symtab_and_line ();
-      symtab_and_line cursal = get_current_source_symtab_and_line ();
-
       /* If this is the first "list" since we've set the current
 	 source line, center the listing around that line.  */
       if (get_first_line_listed () == 0 && (arg == nullptr || arg[0] != '.'))
 	{
-	  list_around_line (arg, cursal);
+	  set_default_source_symtab_and_line ();
+	  list_around_line (arg, get_current_source_symtab_and_line ());
 	}
 
       /* "l" and "l +" lists the next few lines, unless we're listing past
 	 the end of the file.  */
       else if (arg == nullptr || arg[0] == '+')
 	{
+	  set_default_source_symtab_and_line ();
+	  const symtab_and_line cursal = get_current_source_symtab_and_line ();
 	  if (last_symtab_line (cursal.symtab) >= cursal.line)
 	    print_source_lines (cursal.symtab,
 				source_lines_range (cursal.line), 0);
 	  else
-	    {
-	      error (_("End of the file was already reached, use \"list .\" to"
-		       " list the current location again"));
-	    }
+	    error (_("End of the file was already reached, use \"list .\" to"
+		     " list the current location again"));
 	}
 
       /* "l -" lists previous ten lines, the ones before the ten just
 	 listed.  */
       else if (arg[0] == '-')
 	{
+	  set_default_source_symtab_and_line ();
+	  const symtab_and_line cursal = get_current_source_symtab_and_line ();
+
 	  if (get_first_line_listed () == 1)
 	    error (_("Already at the start of %s."),
 		   symtab_to_filename_for_display (cursal.symtab));
+
 	  source_lines_range range (get_first_line_listed (),
 				    source_lines_range::BACKWARD);
 	  print_source_lines (cursal.symtab, range, 0);
@@ -1273,6 +1275,7 @@ list_command (const char *arg, int from_tty)
       /* "list ." lists the default location again.  */
       else if (arg[0] == '.')
 	{
+	  symtab_and_line cursal;
 	  if (target_has_stack ())
 	    {
 	      /* Find the current line by getting the PC of the currently
@@ -1280,18 +1283,34 @@ list_command (const char *arg, int from_tty)
 	      frame_info_ptr frame = get_selected_frame (nullptr);
 	      CORE_ADDR curr_pc = get_frame_pc (frame);
 	      cursal = find_pc_line (curr_pc, 0);
+
+	      if (cursal.symtab == nullptr)
+		error
+		  (_("Insufficient debug info for showing source lines at "
+		     "current PC (%s)."), paddress (get_frame_arch (frame),
+						    curr_pc));
 	    }
 	  else
 	    {
 	      /* The inferior is not running, so reset the current source
 		 location to the default (usually the main function).  */
 	      clear_current_source_symtab_and_line ();
-	      set_default_source_symtab_and_line ();
+	      try
+		{
+		  set_default_source_symtab_and_line ();
+		}
+	      catch (const gdb_exception &e)
+		{
+		  error (_("Insufficient debug info for showing source "
+			   "lines at default location"));
+		}
 	      cursal = get_current_source_symtab_and_line ();
+
+	      gdb_assert (cursal.symtab != nullptr);
 	    }
-	  if (cursal.symtab == nullptr)
-	    error (_("No debug information available to print source lines."));
+
 	  list_around_line (arg, cursal);
+
 	  /* Set the repeat args so just pressing "enter" after using "list ."
 	     will print the following lines instead of the same lines again. */
 	  if (from_tty)