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Re: [RFC] PR 15075 dprintf interferes with "next"


Hi Pedro and Tom,

Thanks for your review.

On Wed, May 22, 2013 at 8:46 PM, Pedro Alves <palves@redhat.com> wrote:
> On 05/22/2013 11:21 AM, Hui Zhu wrote:
>
>> I tried it on fedora and looks it works OK most of times.  I only got
>> trouble is when run this test with remote, [runto main] with
>> "non-stop" is open will fail sometime.
>
> Sorry, but "most of the times" is not acceptable.  Can you please
> figure out why that is so?  This should never fail.

I found a issue about remote test and non-stop.  Because it doesn't
have a lot of relation with dprintf, I will post a separate patch for
that later.

>
>>> > Not sure even that is necessary, given bs->stop==0 and:
>>> >
>>> >       /* Print nothing for this entry if we don't stop or don't
>>> >          print.  */
>>> >       if (!bs->stop || !bs->print)
>>> >         bs->print_it = print_it_noop;
>> I am not sure about this part.
>> If my understanding about Tom's review in before is right, the action
>> of dprintf command should be handled when GDB check the condition.
>> And after that, dprintf not need be handled.
>
> Yes, but I don't see how that counters my suggestion.

Added dprintf_create_breakpoints_sal. When dprintf is created, auto
set silent to 0.

>
>>> >
>>>> >> +  bpstat_do_actions_1 (&bs);
>>>> >> +  bs->next = tmp;
>>>> >> +}
>>> >
>>> > Could you add some comments explaining what this is
>>> > doing, and why?
>> I update this function to following part:
>> /* Implement the "after_cond" breakpoint_ops method for dprintf.  */
>>
>> static void
>> dprintf_after_cond (struct bpstats *bs)
>
>
>> {
>>   struct cleanup *old_chain;
>>   struct breakpoint *b = bs->breakpoint_at;
>>
>>   bs->commands = b->commands;
>>   incref_counted_command_line (bs->commands);
>
> I still think there's no point in moving this to the
> after_condition_true hook, if both existing implementations
> end up doing it themselves.  See below.
>
>>
>>   /* Because function bpstat_do_actions_1 will execute all the command
>>      list of BS and follow it by BS->NEXT, temporarily set BS->NEXT to
>>      NULL.  */
>>   old_chain = make_cleanup_restore_ptr ((void **)&bs->next);
>
> That cast is invalid actually.  Older gcc's will complain about
> the aliasing violation.  I think we can get away without this, by
> passing a separate list with only one entry to bpstat_do_actions_1.
>
>>   bs->next = NULL;
>>   bpstat_do_actions_1 (&bs);
>>   do_cleanups (old_chain);
>>
>>   /* This dprintf need not be handled after this function
>>      because its command list is executed by bpstat_do_actions_1.
>>      Clear STOP and PRINT for that.  */
>>   bs->stop = 0;
>>   bs->print = 0;
>
> Thanks.  I was more looking for general design comments on why we
> run the command list here.  This also should explain why clear stop
> here, instead of on the more natural check_status.
>
> So all in all, if it works for you (seems to work fine for me), I'd
> rather do as this patch on top of yours does:
>

Thanks for this patch.  I merged it to dprintf-continue patch.

> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  gdb/breakpoint.c |   62 ++++++++++++++++++++++++++++++++----------------------
>  1 file changed, 37 insertions(+), 25 deletions(-)
>
> diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
> index 7ef5703..181aecc 100644
> --- a/gdb/breakpoint.c
> +++ b/gdb/breakpoint.c
> @@ -5292,6 +5292,15 @@ bpstat_stop_status (struct address_space *aspace,
>                     b->enable_state = bp_disabled;
>                   removed_any = 1;
>                 }
> +
> +             if (b->silent)
> +               bs->print = 0;
> +             bs->commands = b->commands;
> +             incref_counted_command_line (bs->commands);
> +             if (command_line_is_silent (bs->commands
> +                                         ? bs->commands->commands : NULL))
> +               bs->print = 0;
> +
>               b->ops->after_condition_true (bs);
>             }
>
> @@ -12742,15 +12751,7 @@ base_breakpoint_explains_signal (struct breakpoint *b)
>  static void
>  base_breakpoint_after_condition_true (struct bpstats *bs)
>  {
> -  struct breakpoint *b = bs->breakpoint_at;
> -
> -  if (b->silent)
> -    bs->print = 0;
> -  bs->commands = b->commands;
> -  incref_counted_command_line (bs->commands);
> -  if (command_line_is_silent (bs->commands
> -                             ? bs->commands->commands : NULL))
> -    bs->print = 0;
> +  /* Nothing to do.   */
>  }
>
>  struct breakpoint_ops base_breakpoint_ops =
> @@ -13368,30 +13369,41 @@ dprintf_print_recreate (struct breakpoint *tp, struct ui_file *fp)
>  }
>
>  /* Implement the "after_condition_true" breakpoint_ops method for
> -   dprintf.  */
> +   dprintf.
> +
> +   dprintf's are implemented with regular commands in their command
> +   list, but we run the commands here instead of before presenting the
> +   stop to the user, as dprintf's don't actually cause a stop.  This
> +   also makes it so that the commands of multiple dprintfs at the same
> +   address are all handled.  */
>
>  static void
>  dprintf_after_condition_true (struct bpstats *bs)
>  {
>    struct cleanup *old_chain;
> -  struct breakpoint *b = bs->breakpoint_at;
> +  struct bpstats tmp_bs = { NULL };
> +  struct bpstats *tmp_bs_p = &tmp_bs;
>
> -  bs->commands = b->commands;
> -  incref_counted_command_line (bs->commands);
> +  /* dprintf's never cause a stop.  This wasn't set in the
> +     check_status hook instead because that would make the dprintf's
> +     condition not be evaluated.  */
> +  bs->stop = 0;
>
> -  /* Because function bpstat_do_actions_1 will execute all the command
> -     list of BS and follow it by BS->NEXT, temporarily set BS->NEXT to
> -     NULL.  */
> -  old_chain = make_cleanup_restore_ptr ((void **)&bs->next);
> -  bs->next = NULL;
> -  bpstat_do_actions_1 (&bs);
> -  do_cleanups (old_chain);
> +  /* Run the command list here.  Take ownership of it instead of
> +     copying.  We never want these commands to run later in
> +     bpstat_do_actions, if a breakpoint that causes a stop happens to
> +     be set at same address as this dprintf, or even if running the
> +     commands here throws.  */
> +  tmp_bs.commands = bs->commands;
> +  bs->commands = NULL;
> +  old_chain = make_cleanup_decref_counted_command_line (&tmp_bs.commands);
>
> -  /* This dprintf need not be handled after this function
> -     because its command list is executed by bpstat_do_actions_1.
> -     Clear STOP and PRINT for that.  */
> -  bs->stop = 0;
> -  bs->print = 0;
> +  bpstat_do_actions_1 (&tmp_bs_p);
> +
> +  /* 'tmp_bs.commands' will usually be NULL by now, but
> +     bpstat_do_actions_1 may return early without processing the whole
> +     list.  */
> +  do_cleanups (old_chain);
>  }
>
>  /* The breakpoint_ops structure to be used on static tracepoints with
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>>>> >> +if [prepare_for_testing $expfile $executable $srcfile {debug}] {
>>>> >> +    untested "failed to prepare for trace tests"
>>> >
>>> > This is not a trace test.  Actually, prepare_for_testing
>>> > already calls untested with whatever we pass it as first argument.
>>> > I think it'd be the first such call in the testsuite, but I
>>> > think this would be better:
>>> >
>>> > if [prepare_for_testing "failed to prepare for trace tests" \
>>> >     $executable $srcfile {debug}] {
>>> >    return -1
>>> > }
>> After I use this part of code, I got:
>> ERROR: tcl error sourcing ../../../src/gdb/testsuite/gdb.base/dprintf-next.exp.
>> ERROR: wrong # args: should be "prepare_for_testing testname
>> executable ?sources? ?options?"
>>     while executing
>> "prepare_for_testing "failed to prepare for dprintf next tests""
>>     invoked from within
>> "if [prepare_for_testing "failed to prepare for dprintf next tests"
>>     $executable $srcfile {debug}] {
>>    return -1
>> }"
>
> Hmm?  Oh, it looks like you forgot the '\' at the end of the line.
> Please try again.

Fixed both dprintf-next.exp and dprintf-non-stop.exp.

>
>> So I change this part to:
>> if { [prepare_for_testing dprintf-next.exp "dprintf-next" {} {debug}] } {
>
> 'dprintf-next.exp' really isn't magical.  It's just a string.  :-)
>
>>     return -1
>> }
>
>>>> >> +gdb_test "next" ".*" "next 1"
>>>> >> +gdb_test "next" ".*" "next 2"
>>> >
>>> > Please use more string regexes for these, that confirm the next stopped
>>> > at the right lines.
>> Fixed.
>
> Sorry, I should have been clearer.  Don't do that by checking
> line numbers though, as those change when more functions are
> added to the test.  Just make each line look different instead.
>
>> +
>> +gdb_test "dprintf $dp_location, \"%d\\n\", x" \
>> +    "Dprintf .*"
>
> Please add an explicit 3rd parameter to gdb_test, so that
> the line number doesn't appear in gdb.sum.
>
>> +
>> +gdb_test "next" "23.*\\+\\+x.*" "next 1"
>> +gdb_test "next" "24.*\\+\\+x.*" "next 2"
>
> Do something like this:
>
> gdb_test "next" "\\+\\+x;" "next 1"
> gdb_test "next" "\\+\\+x; /* set dprintf here" "next 2"
>
> You could add a comment to the first stepped line to
> make that clearer:
>
> gdb_test "next" "\\+\\+x; /* step here.*" "next 1"
> gdb_test "next" "\\+\\+x; /* set dprintf here" "next 2"

This part is fixed.

>
>
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.base/dprintf-non-stop.c
>> @@ -0,0 +1,30 @@
>> +/* This testcase is part of GDB, the GNU debugger.
>> +
>> +   Copyright (C) 2013 Free Software Foundation, Inc.
>> +   Contributed by Hui Zhu  <hui@codesourcery.com>
>> +
>> +   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
>> +   the Free Software Foundation; either version 3 of the License, or
>> +   (at your option) any later version.
>> +
>> +   This program is distributed in the hope that it will be useful,
>> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> +   GNU General Public License for more details.
>> +
>> +   You should have received a copy of the GNU General Public License
>> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
>> +
>> +void
>> +foo ()
>> +{
>> +}
>> +
>> +int
>> +main ()
>> +{
>> +  foo ();
>> +  while (1);
>
> If something goes wrong, like GDB crashing, this could leave the test
> running forever, pegging the CPU.  Just make it sleep for some
> time instead.

Changed this part to sleep(3)

>
>> +  return 0;
>
>> +}
>> \ No newline at end of file
>
> Please watch out for these, and add a newline.
>

Fixed.

>> +gdb_test "dprintf foo,\"At foo entry\\n\"" "Dprintf .*"
>> +
>> +send_gdb "continue &\n"
>> +exec sleep 1
>> +set test "interrupt"
>> +gdb_test_multiple $test $test {
>> +    -re "interrupt\r\n$gdb_prompt " {
>> +     pass $test
>> +    }
>> +}
>> +
>> +set test "inferior stopped"
>> +gdb_test_multiple "" $test {
>> +    -re "\r\n\\\[.* \[0-9\]+\\\] #1 stopped\\\.\r\n" {
>> +     pass $test
>> +    }
>> +}
>
> This leaves the prompt in the expect buffer.  I think
> this is likely to confuse the following test that runs.
>

After change this part to:
gdb_test_multiple "" $test {
    -re "\r\n\\\[.* \[0-9\]+\\\] #1 stopped\\\.\r\n$gdb_prompt" {
	pass $test
    }
}
I got:
Running ../../../src/gdb/testsuite/gdb.base/dprintf-non-stop.exp ...
FAIL: gdb.base/dprintf-non-stop.exp: inferior stopped (timeout)

I thought the reason is:
(gdb) PASS: gdb.base/dprintf-non-stop.exp: interrupt

[process 24118] #1 stopped.
0x00002aaaaad8f830 in nanosleep () from /lib/x86_64-linux-gnu/libc.so.6
FAIL: gdb.base/dprintf-non-stop.exp: inferior stopped (timeout)

There is not $gdb_prompt.


On Wed, May 22, 2013 at 10:04 PM, Tom Tromey <tromey@redhat.com> wrote:
>>>>>> "Hui" == Hui Zhu <teawater@gmail.com> writes:
>
> Hui> So I change this part to:
> Hui> if { [prepare_for_testing dprintf-next.exp "dprintf-next" {} {debug}] } {
> Hui>     return -1
> Hui> }
>
> I think it is better to use the variables created by standard_testfile.

Fixed.

The attachments are the new patches.

Best,
Hui

2013-05-28  Yao Qi  <yao@codesourcery.com>
	    Hui Zhu  <hui@codesourcery.com>
	    Pedro Alves  <palves@redhat.com>

	PR breakpoints/15075
	PR breakpoints/15434
	* breakpoint.c (bpstat_stop_status): Call
	b->ops->after_condition_true.
	(update_dprintf_command_list): Don't append "continue" command
	to the command list of dprintf breakpoint.
	(base_breakpoint_after_condition_true): New function.
	(base_breakpoint_ops): Add base_breakpoint_after_condition_true.
	(dprintf_create_breakpoints_sal,
	dprintf_after_condition_true): New functions.
	(initialize_breakpoint_ops): Set dprintf_create_breakpoints_sal
	and dprintf_after_condition_true.
	* breakpoint.h (breakpoint_ops): Add after_condition_true.

2013-05-28  Yao Qi  <yao@codesourcery.com>
	    Hui Zhu  <hui@codesourcery.com>

	PR breakpoints/15075
	PR breakpoints/15434
	* gdb.base/dprintf-next.c: New file.
	* gdb.base/dprintf-next.exp: New file.
	* gdb.base/dprintf-non-stop.c: New file.
	* gdb.base/dprintf-non-stop.exp: New file.
	* gdb.base/dprintf.exp: Don't check "continue" in the output
	of "info breakpoints".
	* gdb.mi/mi-breakpoint-changed.exp (test_insert_delete_modify):
	Don't check "continue" in script field.

Attachment: dprintf-continue.txt
Description: Text document

Attachment: dprintf-continue-test.txt
Description: Text document


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