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Re: [PATCH 2/4]: Handle SIGINT under Python by raising KeyboardInterrupt


>>>>> "Yit" == Khoo Yit Phang <khooyp@cs.umd.edu> writes:

Yit> This turns out the be way more involved than it seems. In particular,
Yit> convert_value_from_python (and it's callers) have nested TRY_CATCHs
Yit> and interleaves calls to Python and calls to GDB. I haven't gone
Yit> through every TRY_CATCH yet, but using these macros won't be that
Yit> simple. I'm inclined to just wrap long-running calls for now.

How about this patch instead?

This one works by partially replacing gdb's mechanism with Python's,
which seems to use the same general idea: set a flag and check it later.

This may result in Python doing a few extra calls to PyErr_CheckSignals,
but I don't think that is a big deal.

I haven't run it through the test suite yet.  I will.

I'd appreciate it if you could give it a try.

Tom

commit 49f1b4e40a0cb0a856ce9a685204be41f63f6571
Author: Tom Tromey <tromey@redhat.com>
Date:   Mon Jul 30 07:54:37 2012 -0600

    use python signal-checking code if available
    
    	* defs.h (quit_flag): Conditionally declare.
    	(clear_quit_flag, check_quit_flag, set_quit_flag): New
    	macros.
    	(QUIT): Use them.
    	* event-top.c (command_handler): Use clear_quit_flag.
    	(handle_sigint): Use set_quit_flag.
    	(async_request_quit): Use check_quit_flag.
    	* exceptions.c (throw_exception): Use clear_quit_flag.
    	* main.c (captured_main): Use clear_quit_flag.
    	* python/python.c (clear_quit_flag, set_quit_flag)
    	(check_quit_flag): New functions.
    	* remote-sim.c (gdb_os_poll_quit): Use check_quit_flag,
    	clear_quit_flag.
    	* remote.c (remote_wait_as): Use check_quit_flag,
    	clear_quit_flag.
    	* symfile.c (load_progress): Use check_quit_flag.
    	* top.c (command_loop): Use clear_quit_flag.
    	* utils.c (quit_flag): Conditionally define.

diff --git a/gdb/defs.h b/gdb/defs.h
index 7be99a2..4ee46da 100644
--- a/gdb/defs.h
+++ b/gdb/defs.h
@@ -171,7 +171,36 @@ extern char *python_libdir;
 /* Search path for separate debug files.  */
 extern char *debug_file_directory;
 
+/* GDB has two methods for handling SIGINT.  When immediate_quit is
+   nonzero, a SIGINT results in an immediate longjmp out of the signal
+   handler.  Otherwise, SIGINT simply sets a flag; code that might
+   take a long time, and which ought to be interruptible, checks this
+   flag using the QUIT macro.
+   
+   If GDB is built with Python support, it uses Python's low-level
+   interface to implement the flag.  This approach makes it possible
+   for Python and GDB SIGINT handling to coexist seamlessly.
+
+   If GDB is built without Python, it instead uses its traditional
+   variables.
+   
+   The distinction between these two cases is hidden behind a few
+   macros, defined here.  */
+
+#ifndef HAVE_PYTHON
 extern int quit_flag;
+/* Clear the quit flag.  */
+#define clear_quit_flag() do { quit_flag = 0; } while (0)
+/* Evaluate to non-zero if the quit flag is set, zero otherwise.  */
+#define check_quit_flag() (quit_flag + 0)
+/* Set the quit flag.  */
+#define set_quit_flag() do { quit_flag = 1; } while (0)
+#else
+extern void clear_quit_flag (void);
+extern int check_quit_flag (void);
+extern void set_quit_flag (void);
+#endif /* HAVE_PYTHON */
+
 extern int immediate_quit;
 
 extern void quit (void);
@@ -184,7 +213,7 @@ extern void quit (void);
    needed.  */
 
 #define QUIT { \
-  if (quit_flag) quit (); \
+  if (check_quit_flag ()) quit (); \
   if (deprecated_interactive_hook) deprecated_interactive_hook (); \
 }
 
diff --git a/gdb/event-top.c b/gdb/event-top.c
index 52e7852..204546d 100644
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -415,7 +415,7 @@ command_handler (char *command)
   int stdin_is_tty = ISATTY (stdin);
   struct cleanup *stat_chain;
 
-  quit_flag = 0;
+  clear_quit_flag ();
   if (instream == stdin && stdin_is_tty)
     reinitialize_more_filter ();
 
@@ -799,7 +799,7 @@ handle_sigint (int sig)
      set quit_flag to 1 here.  Then if QUIT is called before we get to
      the event loop, we will unwind as expected.  */
 
-  quit_flag = 1;
+  set_quit_flag ();
 
   /* If immediate_quit is set, we go ahead and process the SIGINT right
      away, even if we usually would defer this to the event loop.  The
@@ -831,7 +831,7 @@ async_request_quit (gdb_client_data arg)
      is no reason to call quit again here, unless immediate_quit is
      set.  */
 
-  if (quit_flag || immediate_quit)
+  if (check_quit_flag () || immediate_quit)
     quit ();
 }
 
diff --git a/gdb/exceptions.c b/gdb/exceptions.c
index 7db9df9..b7cf9a2 100644
--- a/gdb/exceptions.c
+++ b/gdb/exceptions.c
@@ -221,7 +221,7 @@ exceptions_state_mc_action_iter_1 (void)
 void
 throw_exception (struct gdb_exception exception)
 {
-  quit_flag = 0;
+  clear_quit_flag ();
   immediate_quit = 0;
 
   do_cleanups (all_cleanups ());
diff --git a/gdb/main.c b/gdb/main.c
index d075694..326b101 100644
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -331,7 +331,7 @@ captured_main (void *data)
   dirarg = (char **) xmalloc (dirsize * sizeof (*dirarg));
   ndir = 0;
 
-  quit_flag = 0;
+  clear_quit_flag ();
   saved_command_line = (char *) xmalloc (saved_command_line_size);
   saved_command_line[0] = '\0';
   instream = stdin;
diff --git a/gdb/python/python.c b/gdb/python/python.c
index c66efe4..4a2b518 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -151,6 +151,31 @@ ensure_python_env (struct gdbarch *gdbarch,
   return make_cleanup (restore_python_env, env);
 }
 
+/* Clear the quit flag.  */
+
+void
+clear_quit_flag (void)
+{
+  /* This clears the flag as a side effect.  */
+  PyOS_InterruptOccurred ();
+}
+
+/* Set the quit flag.  */
+
+void
+set_quit_flag (void)
+{
+  PyErr_SetInterrupt ();
+}
+
+/* Return true if the quit flag has been set, false otherwise.  */
+
+int
+check_quit_flag (void)
+{
+  return PyOS_InterruptOccurred ();
+}
+
 /* A wrapper around PyRun_SimpleFile.  FILE is the Python script to run
    named FILENAME.
 
diff --git a/gdb/remote-sim.c b/gdb/remote-sim.c
index f5927f2..d0ba080 100644
--- a/gdb/remote-sim.c
+++ b/gdb/remote-sim.c
@@ -950,9 +950,9 @@ gdb_os_poll_quit (host_callback *p)
   if (deprecated_ui_loop_hook != NULL)
     deprecated_ui_loop_hook (0);
 
-  if (quit_flag)		/* gdb's idea of quit */
+  if (check_quit_flag ())	/* gdb's idea of quit */
     {
-      quit_flag = 0;		/* we've stolen it */
+      clear_quit_flag ();	/* we've stolen it */
       return 1;
     }
   else if (immediate_quit)
diff --git a/gdb/remote.c b/gdb/remote.c
index 6780212..e12f630 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -5714,9 +5714,9 @@ remote_wait_as (ptid_t ptid, struct target_waitstatus *status, int options)
 	  ofunc = signal (SIGINT, remote_interrupt);
 	  /* If the user hit C-c before this packet, or between packets,
 	     pretend that it was hit right here.  */
-	  if (quit_flag)
+	  if (check_quit_flag ())
 	    {
-	      quit_flag = 0;
+	      clear_quit_flag ();
 	      remote_interrupt (SIGINT);
 	    }
 	}
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 95ed480..264ed56 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -1986,7 +1986,7 @@ load_progress (ULONGEST bytes, void *untyped_arg)
   args->buffer += bytes;
   totals->write_count += 1;
   args->section_sent += bytes;
-  if (quit_flag
+  if (check_quit_flag ()
       || (deprecated_ui_load_progress_hook != NULL
 	  && deprecated_ui_load_progress_hook (args->section_name,
 					       args->section_sent)))
diff --git a/gdb/top.c b/gdb/top.c
index 061ad48..10baa32 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -567,7 +567,7 @@ command_loop (void)
       if (window_hook && instream == stdin)
 	(*window_hook) (instream, get_prompt ());
 
-      quit_flag = 0;
+      clear_quit_flag ();
       if (instream == stdin && stdin_is_tty)
 	reinitialize_more_filter ();
       old_chain = make_cleanup (null_cleanup, 0);
diff --git a/gdb/utils.c b/gdb/utils.c
index c69c3e0..036e39e 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -114,9 +114,11 @@ static int debug_timestamp = 0;
 
 int job_control;
 
+#ifndef HAVE_PYTHON
 /* Nonzero means a quit has been requested.  */
 
 int quit_flag;
+#endif /* HAVE_PYTHON */
 
 /* Nonzero means quit immediately if Control-C is typed now, rather
    than waiting until QUIT is executed.  Be careful in setting this;


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