Allow SIGINT to raise KeyboardInterrupt under the "python" command.

gdb/Changelog:

2012-07-16  Khoo Yit Phang <khooyp@cs.umd.edu>

	Allow SIGINT to raise KeyboardInterrupt under the "python" command.
	* python/python-internal.h (gdbpy_suspend_sigint_handler): New
	prototype>
	* python/python.c (gdbpy_saved_sigint_handler): New variable.
	(gdbpy_handle_sigint): New function.
	(gdbpy_restore_sigint_handler): Ditto.
	(gdbpy_install_sigint_handler): Ditto.
	(gdbpy_resume_sigint_handler): Ditto.
	(gdbpy_suspend_sigint_handler): Ditto.
	(restore_python_env): Call gdbpy_install_sigint_handler.
	(ensure_python_env): Call gdbpy_restore_sigint_handler.
	(python_command): Move call to ensure_python_env closer to
	Python entry.
	(execute_gdb_command): Call gdbpy_suspend_sigint_handler.

diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -104,6 +104,8 @@
 
 #include "exceptions.h"
 
+struct cleanup *gdbpy_suspend_sigint_handler (void);
+
 enum gdbpy_iter_kind { iter_keys, iter_values, iter_items };
 
 struct block;
diff --git a/gdb/python/python.c b/gdb/python/python.c
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -97,6 +97,64 @@
 struct gdbarch *python_gdbarch;
 const struct language_defn *python_language;
 
+/* When entering Python, install a Python-specific SIGINT handler;
+   restore the original handler upon exit.  A global variable is
+   used to save GDB's SIGINT handler, such that any changes to the
+   SIGINT handler in a nested GDB context will propagate to the
+   outer GDB context, which is not necessarily the old SIGINT
+   handler. */
+
+static sig_t gdbpy_saved_sigint_handler;
+
+/* SIGINT handler for Python. */
+
+static void
+gdbpy_handle_sigint (int sig)
+{
+  signal (SIGINT, gdbpy_handle_sigint);
+  PyErr_SetInterrupt ();
+}
+
+/* Restore the saved SIGINT handler for GDB before returning from
+   Python. */
+
+static void
+gdbpy_restore_sigint_handler (void)
+{
+  signal (SIGINT, gdbpy_saved_sigint_handler);
+}
+
+/* Save the SIGINT handler for GDB before entering Python, and install
+   the Python SIGINT handler. */
+
+static void
+gdbpy_install_sigint_handler (void)
+{
+  gdbpy_saved_sigint_handler = signal (SIGINT, gdbpy_handle_sigint);
+}
+
+/* Cleanup function that restores the Python SIGINT handler. Note that
+   this propagates the current SIGINT handler for GDB down to the
+   outer GDB context. */
+
+static void
+gdbpy_resume_sigint_handler (void *s)
+{
+  gdbpy_install_sigint_handler ();
+}
+
+/* Temporarily suspend the Python SIGINT handler and restore the
+   saved SIGINT handler for GDB before entering GDB. (Currently, only
+   called by gdb.execute since it's most likely to take a long
+   time.) */
+
+struct cleanup *
+gdbpy_suspend_sigint_handler (void)
+{
+  gdbpy_restore_sigint_handler ();
+  return make_cleanup (gdbpy_resume_sigint_handler, NULL);
+}
+
 /* Restore global language and architecture and Python GIL state
    when leaving the Python interpreter.  */
 
@@ -123,6 +181,8 @@
 
   PyErr_Restore (env->error_type, env->error_value, env->error_traceback);
 
+  gdbpy_restore_sigint_handler ();
+
   PyGILState_Release (env->state);
   python_gdbarch = env->gdbarch;
   python_language = env->language;
@@ -142,6 +202,8 @@
   env->gdbarch = python_gdbarch;
   env->language = python_language;
 
+  gdbpy_install_sigint_handler ();
+
   python_gdbarch = gdbarch;
   python_language = language;
 
@@ -322,15 +384,15 @@
 {
   struct cleanup *cleanup;
 
-  cleanup = ensure_python_env (get_current_arch (), current_language);
-
-  make_cleanup_restore_integer (&interpreter_async);
+  cleanup = make_cleanup_restore_integer (&interpreter_async);
   interpreter_async = 0;
 
   while (arg && *arg && isspace (*arg))
     ++arg;
   if (arg && *arg)
     {
+      ensure_python_env (get_current_arch (), current_language);
+
       if (PyRun_SimpleString (arg))
 	error (_("Error while executing Python code."));
     }
@@ -503,6 +565,7 @@
       char *copy = xstrdup (arg);
       struct cleanup *cleanup = make_cleanup (xfree, copy);
 
+      gdbpy_suspend_sigint_handler ();
       make_cleanup_restore_integer (&interpreter_async);
       interpreter_async = 0;