[PATCH v2 3/3] [gdb/tui] Allow second tui enable if first fails

[Tom de Vries <tdevries@suse.de>]

Commit fb23d7ba4a2 ("[gdb/tui] Handle error in tui_enable") handles a
particular error during tui_enable, but doesn't allow trying to enable TUI
again.

I tried to get this to work, but didn't manage because I didn't understand the
interaction between endwin and the "tui_batch_rendering defer" destructor:
- first endwin restores the shell terminal mode
- then the defer destructor calls doupdate, restoring program terminal mode.

Fix this by checking for tui_active in ~tui_batch_rendering.
---
 gdb/tui/tui-wingeneral.c | 2 +-
 gdb/tui/tui.c            | 9 +++++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/gdb/tui/tui-wingeneral.c b/gdb/tui/tui-wingeneral.c
index 86f13d275b4..149ca4efc6e 100644
--- a/gdb/tui/tui-wingeneral.c
+++ b/gdb/tui/tui-wingeneral.c
@@ -46,7 +46,7 @@ tui_batch_rendering::tui_batch_rendering ()
 tui_batch_rendering::~tui_batch_rendering ()
 {
   suppress_output = m_saved_suppress;
-  if (!suppress_output)
+  if (!suppress_output && tui_active)
     doupdate ();
 }
 
diff --git a/gdb/tui/tui.c b/gdb/tui/tui.c
index 11bcba813bc..958fc47b7b6 100644
--- a/gdb/tui/tui.c
+++ b/gdb/tui/tui.c
@@ -494,7 +494,7 @@ tui_enable (void)
       /* Don't try initialization again.  */
       tui_finish_init = TRIBOOL_UNKNOWN;
 
-      SCREEN *s = init_ncurses ();
+      init_ncurses ();
       w = stdscr;
 
       if (has_colors ())
@@ -532,8 +532,13 @@ tui_enable (void)
       catch (const gdb_exception &)
 	{
 	  endwin ();
-	  delscreen (s);
+
+	  /* Initialization failed, so TUI is not active.  */
 	  tui_active = false;
+
+	  /* Allow trying to initialize TUI again.  */
+	  tui_finish_init = TRIBOOL_TRUE;
+
 	  throw;
 	}
 
-- 
2.51.0