Don't allow switching on the TUI in some cases

[Pedro Alves <pedro@codesourcery.com>]

A slightly updated patch originally posted at:
<http://sourceware.org/ml/gdb-patches/2010-03/msg01085.html>

Tested on x86_64-linux and checked in.

-- 
Pedro Alves

2010-03-30  Pedro Alves  <pedro@codesourcery.com>

	* tui/tui-interp.c (tui_is_toplevel): New.
	(tui_init): Set it.
	(tui_allowed_p): New.
	* tui/tui.c (tui_enable): Check if the TUI is allowed before
	enabling it.
	* tui/tui.h (tui_allowed_p): Declare.

---
 gdb/tui/tui-interp.c |   17 +++++++++++++++++
 gdb/tui/tui.c        |    3 +++
 gdb/tui/tui.h        |    4 ++++
 3 files changed, 24 insertions(+)

Index: src/gdb/tui/tui-interp.c
===================================================================
--- src.orig/gdb/tui/tui-interp.c	2010-03-30 21:40:50.000000000 +0100
+++ src/gdb/tui/tui-interp.c	2010-03-30 22:44:05.000000000 +0100
@@ -45,11 +45,16 @@ tui_exit (void)
   tui_disable ();
 }
 
+/* True if TUI is the top-level interpreter.  */
+static int tui_is_toplevel = 0;
+
 /* These implement the TUI interpreter.  */
 
 static void *
 tui_init (int top_level)
 {
+  tui_is_toplevel = top_level;
+
   /* Install exit handler to leave the screen in a good shape.  */
   atexit (tui_exit);
 
@@ -63,6 +68,18 @@ tui_init (int top_level)
   return NULL;
 }
 
+/* True if enabling the TUI is allowed.  Example, if the top level
+   interpreter is MI, enabling curses will certainly lose.  */
+
+int
+tui_allowed_p (void)
+{
+  /* Only if TUI is the top level interpreter.  Also don't try to
+     setup curses (and print funny control characters) if we're not
+     outputting to a terminal.  */
+  return tui_is_toplevel && ui_file_isatty (gdb_stdout);
+}
+
 static int
 tui_resume (void *data)
 {
Index: src/gdb/tui/tui.c
===================================================================
--- src.orig/gdb/tui/tui.c	2010-03-30 21:40:50.000000000 +0100
+++ src/gdb/tui/tui.c	2010-03-30 22:39:28.000000000 +0100
@@ -364,6 +364,9 @@ tui_initialize_readline (void)
 void
 tui_enable (void)
 {
+  if (!tui_allowed_p ())
+    error (_("TUI mode not allowed"));
+
   if (tui_active)
     return;
 
Index: src/gdb/tui/tui.h
===================================================================
--- src.orig/gdb/tui/tui.h	2010-03-30 21:40:50.000000000 +0100
+++ src/gdb/tui/tui.h	2010-03-30 22:39:28.000000000 +0100
@@ -65,6 +65,10 @@ extern int tui_get_command_dimension (un
    key shortcut.  */
 extern void tui_initialize_readline (void);
 
+/* True if enabling the TUI is allowed.  Example, if the top level
+   interpreter is MI, enabling curses will certainly lose.  */
+extern int tui_allowed_p (void);
+
 /* Enter in the tui mode (curses).  */
 extern void tui_enable (void);