Re: PATCH: PR tui/2173: Arrow keys no longer works in breakpoint command list

[Daniel Jacobowitz <drow@false.org>]

On Tue, Dec 26, 2006 at 07:00:28AM +0100, Jan Kratochvil wrote:
> Here is one which forks for me but still it is more complicated than I expected.
> 
> I believe there may be side effects but unfortunately it can be expected the
> interactive readline(3) usage is not well covered by the testsuite.
> readline(3) call does a lot of various initializations currently omitted by the
> callback-based gdb reimplementation.

I simplified your testcase a bit, and cleaned up code formatting.
Unfortunately, while testing it, I got failures for the other
readline tests in the testsuite (for operate-and-get-next).  The
result of operate-and-get-next gets written out before the prompt
instead of after.

The comments make it pretty clear why it doesn't work:

   At the ordinary top-level prompt we might be using the async
   readline.  That means we can't use rl_pre_input_hook, since it
   doesn't work properly in async mode.

So I also needed a bit of fiddling around with the hooks to get that
to pass.  Which gave me this patch.  I've tested it on
x86_64-pc-linux-gnu and checked it in.  GDB no longer contains any
calls to the synchronous readline().

-- 
Daniel Jacobowitz
CodeSourcery

2007-01-03  Jan Kratochvil  <jan.kratochvil@redhat.com>
	    Daniel Jacobowitz  <dan@codesourcery.com>

	* Makefile.in (top.o): Update.
	* top.c (gdb_readline_wrapper_done, gdb_readline_wrapper_result)
	(saved_after_char_processing_hook, gdb_readline_wrapper_line)
	(struct gdb_readline_wrapper_cleanup, gdb_readline_wrapper_cleanup):
	New.
	(gdb_readline_wrapper): Rewrite to use asynchronous readline.

2007-01-03  Jan Kratochvil  <jan.kratochvil@redhat.com>
	    Daniel Jacobowitz  <dan@codesourcery.com>

	* gdb.base/readline.exp: Set $TERM.  Test arrow keys in
	secondary prompts.

Index: Makefile.in
===================================================================
RCS file: /cvs/src/src/gdb/Makefile.in,v
retrieving revision 1.864
diff -u -p -r1.864 Makefile.in
--- Makefile.in	3 Jan 2007 18:05:43 -0000	1.864
+++ Makefile.in	3 Jan 2007 21:22:46 -0000
@@ -2782,7 +2782,7 @@ top.o: top.c $(defs_h) $(gdbcmd_h) $(cal
 	$(annotate_h) $(completer_h) $(top_h) $(version_h) $(serial_h) \
 	$(doublest_h) $(gdb_assert_h) $(readline_h) $(readline_history_h) \
 	$(event_top_h) $(gdb_string_h) $(gdb_stat_h) $(ui_out_h) \
-	$(cli_out_h) $(main_h)
+	$(cli_out_h) $(main_h) $(event_loop_h)
 tracepoint.o: tracepoint.c $(defs_h) $(symtab_h) $(frame_h) $(gdbtypes_h) \
 	$(expression_h) $(gdbcmd_h) $(value_h) $(target_h) $(language_h) \
 	$(gdb_string_h) $(inferior_h) $(tracepoint_h) $(remote_h) \
Index: top.c
===================================================================
RCS file: /cvs/src/src/gdb/top.c,v
retrieving revision 1.116
diff -u -p -r1.116 top.c
--- top.c	1 Jan 2007 05:57:49 -0000	1.116
+++ top.c	3 Jan 2007 21:22:47 -0000
@@ -47,6 +47,7 @@
 #include "doublest.h"
 #include "gdb_assert.h"
 #include "main.h"
+#include "event-loop.h"
 
 /* readline include files */
 #include "readline/readline.h"
@@ -712,26 +713,111 @@ The filename in which to record the comm
 }
 
 /* This is like readline(), but it has some gdb-specific behavior.
-   gdb can use readline in both the synchronous and async modes during
+   gdb may want readline in both the synchronous and async modes during
    a single gdb invocation.  At the ordinary top-level prompt we might
    be using the async readline.  That means we can't use
    rl_pre_input_hook, since it doesn't work properly in async mode.
    However, for a secondary prompt (" >", such as occurs during a
-   `define'), gdb just calls readline() directly, running it in
-   synchronous mode.  So for operate-and-get-next to work in this
-   situation, we have to switch the hooks around.  That is what
-   gdb_readline_wrapper is for.  */
+   `define'), gdb wants a synchronous response.
+
+   We used to call readline() directly, running it in synchronous
+   mode.  But mixing modes this way is not supported, and as of
+   readline 5.x it no longer works; the arrow keys come unbound during
+   the synchronous call.  So we make a nested call into the event
+   loop.  That's what gdb_readline_wrapper is for.  */
+
+/* A flag set as soon as gdb_readline_wrapper_line is called; we can't
+   rely on gdb_readline_wrapper_result, which might still be NULL if
+   the user types Control-D for EOF.  */
+static int gdb_readline_wrapper_done;
+
+/* The result of the current call to gdb_readline_wrapper, once a newline
+   is seen.  */
+static char *gdb_readline_wrapper_result;
+
+/* Any intercepted hook.  Operate-and-get-next sets this, expecting it
+   to be called after the newline is processed (which will redisplay
+   the prompt).  But in gdb_readline_wrapper we will not get a new
+   prompt until the next call, or until we return to the event loop.
+   So we disable this hook around the newline and restore it before we
+   return.  */
+static void (*saved_after_char_processing_hook) (void);
+
+/* This function is called when readline has seen a complete line of
+   text.  */
+
+static void
+gdb_readline_wrapper_line (char *line)
+{
+  gdb_assert (!gdb_readline_wrapper_done);
+  gdb_readline_wrapper_result = line;
+  gdb_readline_wrapper_done = 1;
+
+  /* Prevent operate-and-get-next from acting too early.  */
+  saved_after_char_processing_hook = after_char_processing_hook;
+  after_char_processing_hook = NULL;
+}
+
+struct gdb_readline_wrapper_cleanup
+  {
+    void (*handler_orig) (char *);
+    char *prompt_orig;
+    int already_prompted_orig;
+  };
+
+static void
+gdb_readline_wrapper_cleanup (void *arg)
+{
+  struct gdb_readline_wrapper_cleanup *cleanup = arg;
+
+  gdb_assert (rl_already_prompted == 1);
+  rl_already_prompted = cleanup->already_prompted_orig;
+  PROMPT (0) = cleanup->prompt_orig;
+
+  gdb_assert (input_handler == gdb_readline_wrapper_line);
+  input_handler = cleanup->handler_orig;
+  gdb_readline_wrapper_result = NULL;
+  gdb_readline_wrapper_done = 0;
+
+  after_char_processing_hook = saved_after_char_processing_hook;
+  saved_after_char_processing_hook = NULL;
+
+  xfree (cleanup);
+}
+
 char *
 gdb_readline_wrapper (char *prompt)
 {
-  /* Set the hook that works in this case.  */
+  struct cleanup *back_to;
+  struct gdb_readline_wrapper_cleanup *cleanup;
+  char *retval;
+
+  cleanup = xmalloc (sizeof (*cleanup));
+  cleanup->handler_orig = input_handler;
+  input_handler = gdb_readline_wrapper_line;
+
+  cleanup->prompt_orig = get_prompt ();
+  PROMPT (0) = prompt;
+  cleanup->already_prompted_orig = rl_already_prompted;
+
+  back_to = make_cleanup (gdb_readline_wrapper_cleanup, cleanup);
+
+  /* Display our prompt and prevent double prompt display.  */
+  display_gdb_prompt (NULL);
+  rl_already_prompted = 1;
+
   if (after_char_processing_hook)
-    {
-      rl_pre_input_hook = (Function *) after_char_processing_hook;
-      after_char_processing_hook = NULL;
-    }
+    (*after_char_processing_hook) ();
+  gdb_assert (after_char_processing_hook == NULL);
 
-  return readline (prompt);
+  /* gdb_do_one_event argument is unused.  */
+  while (gdb_do_one_event (NULL) >= 0)
+    if (gdb_readline_wrapper_done)
+      break;
+
+  retval = gdb_readline_wrapper_result;
+  do_cleanups (back_to);
+  return retval;
 }
 
 \f
Index: testsuite/gdb.base/readline.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.base/readline.exp,v
retrieving revision 1.2
diff -u -p -r1.2 readline.exp
--- testsuite/gdb.base/readline.exp	8 Jun 2003 13:14:05 -0000	1.2
+++ testsuite/gdb.base/readline.exp	3 Jan 2007 21:22:47 -0000
@@ -1,4 +1,4 @@
-# Copyright 2002 Free Software Foundation, Inc.
+# Copyright 2002, 2003, 2007 Free Software Foundation, Inc.
 
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -159,6 +159,14 @@ if [info exists env(INPUTRC)] {
 }
 set env(INPUTRC) "/dev/null"
 
+# The arrow key test relies on the standard VT100 bindings, so make
+# sure that an appropriate terminal is selected.  The same bug
+# doesn't show up if we use ^P / ^N instead.
+if [info exists env(TERM)] {
+    set old_term $env(TERM)
+}
+set env(TERM) "vt100"
+
 gdb_start
 gdb_reinitialize_dir $srcdir/$subdir
 
@@ -178,6 +186,18 @@ operate_and_get_next "operate-and-get-ne
   "p 5" "" \
   "end" ".* = 5"
 
+# Verify that arrow keys work in secondary prompts.  The control
+# sequence is a hard-coded VT100 up arrow.
+gdb_test "print 42" "\\\$\[0-9\]* = 42"
+set msg "arrow keys with secondary prompt"
+gdb_test_multiple "if 1 > 0\n\033\[A\033\[A\nend" $msg {
+    -re ".*\\\$\[0-9\]* = 42\r\n$gdb_prompt $" {
+	pass $msg
+    }
+    -re ".*Undefined command:.*$gdb_prompt $" {
+	fail $msg
+    }
+}
 
 # Now repeat the first test with a history file that fills the entire
 # history list.