[RFA/RFC] fix bug: TUI not print source after switch from source type to command type

[Hui Zhu <teawater at gmail dot com>]

Hi guys,

I found this bug in a long time.  I suggest this bug can be fixed
before 7.2 release.

gdb ./gdb
(top-gdb) start
Temporary breakpoint 3 at 0x409073: file ../../src/gdb/gdb.c, line 29.
Starting program: /home/teawater/gdb/bgdbnotk/gdb/gdb
[Thread debugging using libthread_db enabled]

Temporary breakpoint 3, main (argc=
During symbol reading, incomplete CFI data; unspecified registers
(e.g., rax) at 0x409068.
1, argv=0x7fffffffe298) at ../../src/gdb/gdb.c:29
29	  memset (&args, 0, sizeof args);
(top-gdb)

Ctrl-x a
Switch to source mode.

Use up and down key to move the code.

Ctrl-x a
Switch back to command mode.

Temporary breakpoint 3, main (argc=
During symbol reading, incomplete CFI data; unspecified registers
(e.g., rax) at 0x409068.
1, argv=0x7fffffffe298) at ../../src/gdb/gdb.c:29
29	  memset (&args, 0, sizeof args);
(top-gdb) n
31	in ../../src/gdb/gdb.c
(top-gdb) n
32	in ../../src/gdb/gdb.c
(top-gdb)
33	in ../../src/gdb/gdb.c
(top-gdb)
It cannot output the source code.

The cause of this bug is in print_source_lines_base:
When tui in source mode, Use up and down key to move the code.  The
"tui_vertical_source_scroll" will call "print_source_lines_base".
In it:
  if (ui_out_test_flags (uiout, ui_source_list))
    {
      /* Only prints "No such file or directory" once */
      if ((s != last_source_visited) || (!last_source_error))
	{
	  last_source_visited = s;
	  desc = open_source_file (s);
	}
      else
	{
	  desc = last_source_error;
	  noerror = 1;
	}
    }
  else
    {
      desc = -1;
      noerror = 1;
    }

  if (desc < 0)
    {
      last_source_error = desc;

"ui_out_test_flags (uiout, ui_source_list)" will return false, then
last_source_error will be set to -1.
Then when we set back to command line mode.  The last_source_error
will make this function cannot output the source code.

I have 2 ways to handle this issue:
1.  Looks "print_source_lines_base" is useless for
"tui_vertical_source_scroll".  Maybe we can remove it.
2.  Add a special check for noprint.  I make a patch for it.

Please give me comments about this issue.  Thanks.

Best regards,
Hui


2010-07-05  Hui Zhu  <teawater@gmail.com>

	* source.c (print_source_lines_base): Add check for noprint.


---
 source.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/source.c
+++ b/source.c
@@ -1293,6 +1293,7 @@ print_source_lines_base (struct symtab *
 {
   int c;
   int desc;
+  int noprint = 0;
   FILE *stream;
   int nlines = stopline - line;
   struct cleanup *cleanup;
@@ -1319,11 +1320,12 @@ print_source_lines_base (struct symtab *
     }
   else
     {
-      desc = -1;
+      desc = last_source_error;
       noerror = 1;
+      noprint = 1;
     }

-  if (desc < 0)
+  if (desc < 0 || noprint)
     {
       last_source_error = desc;