Don't allow new-ui to start the TUI

The TUI can't really work properly with new-ui, at least not as
currently written.  This patch changes new-ui to reject an attempt.
Attempting to make a DAP ui this way is also now rejected.

Regression tested on x86-64 Fedora 38.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29273
Approved-By: Andrew Burgess <aburgess@redhat.com>

gdb/interps.c

@@ -187,13 +187,16 @@ interp_lookup (struct ui *ui, const char *name)
 /* See interps.h.  */
 
 void
-set_top_level_interpreter (const char *name)
+set_top_level_interpreter (const char *name, bool for_new_ui)
 {
   /* Find it.  */
   struct interp *interp = interp_lookup (current_ui, name);
 
   if (interp == NULL)
     error (_("Interpreter `%s' unrecognized"), name);
+  if (for_new_ui && !interp->supports_new_ui ())
+    error (_("interpreter '%s' cannot be used with a new UI"), name);
+
   /* Install it.  */
   interp_set (interp, true);
 }

gdb/interps.h

@@ -84,6 +84,10 @@ class interp : public intrusive_list_node<interp>
   virtual bool supports_command_editing ()
   { return false; }
 
+  /* Returns true if this interpreter supports new UIs.  */
+  virtual bool supports_new_ui () const
+  { return true; }
+
   const char *name () const
   { return m_name; }
 
@@ -201,8 +205,10 @@ extern struct interp *interp_lookup (struct ui *ui, const char *name);
 
 /* Set the current UI's top level interpreter to the interpreter named
    NAME.  Throws an error if NAME is not a known interpreter or the
-   interpreter fails to initialize.  */
-extern void set_top_level_interpreter (const char *name);
+   interpreter fails to initialize.  FOR_NEW_UI is true when called
+   from the 'new-ui' command, and causes an extra check to ensure the
+   interpreter is valid for a new UI.  */
+extern void set_top_level_interpreter (const char *name, bool for_new_ui);
 
 /* Temporarily set the current interpreter, and reset it on
    destruction.  */

gdb/main.c

@@ -1147,7 +1147,7 @@ captured_main_1 (struct captured_main_args *context)
 
   /* Install the default UI.  All the interpreters should have had a
      look at things by now.  Initialize the default interpreter.  */
-  set_top_level_interpreter (interpreter_p.c_str ());
+  set_top_level_interpreter (interpreter_p.c_str (), false);
 
   /* The interpreter should have installed the real uiout by now.  */
   gdb_assert (current_uiout != temp_uiout.get ());

gdb/python/py-dap.c

@@ -62,6 +62,9 @@ class dap_interp final : public interp
 
   void pre_command_loop () override;
 
+  bool supports_new_ui () const override
+  { return false; }
+
 private:
 
   std::unique_ptr<ui_out> m_ui_out;

gdb/testsuite/gdb.base/new-ui.exp

@@ -183,6 +183,11 @@ proc_with_prefix do_test_invalid_args {} {
 	     "Interpreter `bloop' unrecognized" \
 	     "new-ui with bad interpreter name"
 
+    # Test that the TUI cannot be used for a new UI.
+    gdb_test "new-ui tui $extra_tty_name" \
+	"interpreter 'tui' cannot be used with a new UI" \
+	"new-ui with tui"
+
     # Test that we can continue working normally.
     if ![runto_main] {
 	return

gdb/tui/tui-interp.c

@@ -50,6 +50,9 @@ class tui_interp final : public cli_interp_base
   void suspend () override;
   void exec (const char *command_str) override;
   ui_out *interp_ui_out () override;
+
+  bool supports_new_ui () const override
+  { return false; }
 };
 
 /* Cleanup the tui before exiting.  */

gdb/ui.c

@@ -224,7 +224,7 @@ new_ui_command (const char *args, int from_tty)
 
     current_ui = ui.get ();
 
-    set_top_level_interpreter (interpreter_name);
+    set_top_level_interpreter (interpreter_name, true);
 
     top_level_interpreter ()->pre_command_loop ();