[binutils-gdb] [gdb/tui] Handle error in tui_enable

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=fb23d7ba4a21c8278f29b7a3d2c4b2cd5c88560d

commit fb23d7ba4a21c8278f29b7a3d2c4b2cd5c88560d
Author: Tom de Vries <[email protected]>
Date:   Tue Apr 28 16:36:34 2026 +0200

    [gdb/tui] Handle error in tui_enable
    
    Say we simulate an error:
    ...
    static void error_once () {
      static int v = 0;
      if (v == 1)
        return;
    
      v = 1;
      error (_("Oh no!!!"));
    }
    ...
    in the call to tui_set_initial_layout in tui_enable:
    ...
           tui_show_frame_info (deprecated_safe_get_selected_frame ());
    +      error_once ();
           tui_set_initial_layout ();
    ...
    
    After doing "tui enable"
    ...
    $ gdb
    (gdb) tui enable
    ...
    the screen is cleared, and we have:
    ...
    ❌️ Oh no!!!
               (gdb) <blinking cursor>
    ...
    
    After typing "apropos tui" (which is not echoed) and pressing enter, I run into
    a segmentation violation here in tui_inject_newline_into_command_window:
    ...
        at /data/vries/gdb/leap-16-0/build/../../src/gdb/tui/tui-io.c:1084
    1084      WINDOW *w = tui_cmd_win ()->handle.get ();
    ...
    because:
    ...
    $2 = (tui_cmd_window *) 0x0
    (gdb) p tui_cmd_win ()
    ...
    
    The problem is that tui_active is true, and so
    tui_inject_newline_into_command_window get called:
    ...
    static void
    tui_command_line_handler (gdb::unique_xmalloc_ptr<char> &&rl)
    {
     ...
      if (tui_active)
        tui_inject_newline_into_command_window ();
     ...
    }
    ...
    
    Fix this by catching the error in tui_enable, and resetting tui_active back to
    false.
    
    While this fixes the segmentation fault, and does allow "apropos tui" to run,
    still the command is not echoed, and the output of the command is garbled by
    runaway indentation.
    
    Fix this by using endwin / delscreen, as borrowed from earlier in tui_enable:
    ...
          if (cap == NULL || cap == (char *) -1 || *cap == '\0')
            {
              endwin ();
              delscreen (s);
              error (_("Cannot enable the TUI: "
                       "terminal doesn't support cursor addressing [TERM=%s]"),
                     gdb_getenv_term ());
            }
    ...
    
    Note that this doesn't allow a second attempt:
    ...
    $ gdb -q
    (gdb) tui enable
    ❌️ Oh no!!!
    (gdb) tui enable
    ❌️ Cannot enable the TUI
    (gdb)
    ...
    because tui_finish_init is stuck at TRIBOOL_UNKNOWN.
    
    IWBN to fix this in a way that allows the second "tui enable" to succeed.  I
    tried this for a bit, but didn't get it to work.
    
    Tested on x86_64-linux.
    
    Suggested-By: Tom Tromey <[email protected]> [1]
    Approved-By: Tom Tromey <[email protected]>
    
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34100
    
    [1] https://sourceware.org/pipermail/gdb-patches/2025-May/217660.html

Diff:
---
 gdb/tui/tui.c | 39 ++++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/gdb/tui/tui.c b/gdb/tui/tui.c
index 35c3b80603d..ba4f6f68769 100644
--- a/gdb/tui/tui.c
+++ b/gdb/tui/tui.c
@@ -491,22 +491,31 @@ tui_enable (void)
 	 rely on this flag being true in order to know that the window
 	 they are creating is currently valid.  */
       tui_active = true;
+      try
+	{
+	  cbreak ();
+	  noecho ();
+	  /* timeout (1); */
+	  nodelay (w, FALSE);
+	  nl ();
+	  keypad (w, TRUE);
+	  tui_set_term_height_to (LINES);
+	  tui_set_term_width_to (COLS);
+	  def_prog_mode ();
+	  tui_show_frame_info (deprecated_safe_get_selected_frame ());
+	  tui_set_initial_layout ();
+	  tui_set_win_focus_to (tui_src_win ());
+	  keypad (tui_cmd_win ()->handle.get (), TRUE);
+	  wrefresh (tui_cmd_win ()->handle.get ());
+	}
+      catch (const gdb_exception &)
+	{
+	  endwin ();
+	  delscreen (s);
+	  tui_active = false;
+	  throw;
+	}
 
-      cbreak ();
-      noecho ();
-      /* timeout (1); */
-      nodelay(w, FALSE);
-      nl();
-      keypad (w, TRUE);
-      tui_set_term_height_to (LINES);
-      tui_set_term_width_to (COLS);
-      def_prog_mode ();
-
-      tui_show_frame_info (deprecated_safe_get_selected_frame ());
-      tui_set_initial_layout ();
-      tui_set_win_focus_to (tui_src_win ());
-      keypad (tui_cmd_win ()->handle.get (), TRUE);
-      wrefresh (tui_cmd_win ()->handle.get ());
       tui_finish_init = TRIBOOL_FALSE;
     }
   else