Clean up source file error reporting

print_source_lines_base reopens the source file every time that a
source line is to be printed.  However, there's no need to do this so
frequently -- it's enough to do it when switching source files, and
otherwise rely on the cache.

The code seems to try to avoid these multiple opens; at a guess I'd
say something just got confused along the way.

This patch fixes the problem by reorganizing the code both to make it
more clear, and to ensure that reopens only occur when the "last
source visited" changes.

gdb/ChangeLog
2019-08-06  Tom Tromey  <tromey@adacore.com>

	* source.c (last_source_error): Now bool.
	(print_source_lines_base): Make "noprint" bool.  Only open
	source file when last_source_visited changes.

1 files changed, 12 insertions, 14 deletions

diff --git a/gdb/source.c b/gdb/source.c
index e0050f1..066666c 100644
--- a/gdb/source.c
+++ b/gdb/source.c
@@ -129,7 +129,7 @@ static int first_line_listed;
    Used to prevent repeating annoying "No such file or directories" msgs.  */
 
 static struct symtab *last_source_visited = NULL;
-static int last_source_error = 0;
+static bool last_source_error = false;
 
 /* Return the first line listed by print_source_lines.
    Used by command interpreters to request listing from
@@ -1129,8 +1129,7 @@ static void
 print_source_lines_base (struct symtab *s, int line, int stopline,
 			 print_source_lines_flags flags)
 {
-  scoped_fd desc;
-  int noprint = 0;
+  bool noprint = false;
   int nlines = stopline - line;
   struct ui_out *uiout = current_uiout;
 
@@ -1144,26 +1143,27 @@ print_source_lines_base (struct symtab *s, int line, int stopline,
   if (uiout->test_flags (ui_source_list))
     {
       /* Only prints "No such file or directory" once.  */
-      if ((s != last_source_visited) || (!last_source_error))
+      if (s == last_source_visited)
 	{
-	  last_source_visited = s;
-	  desc = open_source_file (s);
-	  if (desc.get () < 0)
+	  if (last_source_error)
 	    {
-	      last_source_error = desc.get ();
-	      noprint = 1;
+	      flags |= PRINT_SOURCE_LINES_NOERROR;
+	      noprint = true;
 	    }
 	}
       else
 	{
-	  flags |= PRINT_SOURCE_LINES_NOERROR;
-	  noprint = 1;
+	  last_source_visited = s;
+	  scoped_fd desc = open_source_file (s);
+	  last_source_error = desc.get () < 0;
+	  if (last_source_error)
+	    noprint = true;
 	}
     }
   else
     {
       flags |= PRINT_SOURCE_LINES_NOERROR;
-      noprint = 1;
+      noprint = true;
     }
 
   if (noprint)
@@ -1209,8 +1209,6 @@ print_source_lines_base (struct symtab *s, int line, int stopline,
       return;
     }
 
-  last_source_error = 0;
-
   /* If the user requested a sequence of lines that seems to go backward
      (from high to low line numbers) then we don't print anything.  */
   if (stopline <= line)