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

Daniel Jacobowitz
2007-01-03T21:46:49Z

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.