Re: [PATCH] [gdb/testsuite] Fix gdb.tui/wrap-line.exp

[Andrew Burgess <aburgess@redhat.com>]

Tom de Vries <tdevries@suse.de> writes:

> On 5/21/23 18:48, Tom de Vries wrote:
>> On 5/21/23 10:51, Andrew Burgess wrote:
>>> Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> writes:
>>>
>>>> PR testsuite/30458 reports the following FAIL:
>>>> ...
>>>> PASS: gdb.tui/wrap-line.exp: width-auto-detected: cli: wrap
>>>> ^CQuit
>>>> (gdb) WARNING: timeout in accept_gdb_output
>>>> Screen Dump (size 50 columns x 24 rows, cursor at column 6, row 3):
>>>>      0 Quit
>>>>      1 (gdb) 7890123456789012345678901234567890123456789
>>>>      2 W^CQuit
>>>>      3 (gdb)
>>>>    ...
>>>> FAIL: gdb.tui/wrap-line.exp: width-auto-detected: cli: prompt after wrap
>>>> ...
>>>>
>>>> The problem is that the regexp doesn't account for the ^C:
>>>> ...
>>>>      gdb_assert { [Term::wait_for "^WQuit"] } "prompt after wrap"
>>>> ...
>>>>
>>>> Fix this by updating the regexp, and likewise in another place in the
>>>> test-case where we use ^C.
>>>
>>> Do we know why we sometimes manage to see '^C'?  I guess it's a timing
>>> thing, but right now I'm at a loss for how we manage to see it.  It
>>> appears that we print the wrapping line, that ends with 'W', and then
>>> wait for this to be displayed.
>>>
>>> At this point GDB should be in a stable state waiting in the
>>> event-loop.
>>>
>>> When we send \003 this should trigger an event, which should trigger
>>> async_request_quit, which should result in the 'Quit' exception being
>>> thrown, caught, and printed.
>>>
>>> I think the '^C' must be getting printed from tui_redisplay_readline
>>> maybe, but I can't see how that gets triggered with \003 in the input
>>> buffer.
>>>
>>> I only ask because if we understand why '^C' is sometimes printed then
>>> we might be able to decide if this should always be printed, or never be
>>> printed, and change GDB accordingly...
>>>
>> 
>> Hi Andrew,
>> 
>> yes, that's a good question.
>> 
>> [ Note that it's a TUI test-case, but the FAIL we're observing is in the 
>> cli part, before activating TUI, so tui_redisplay_readline has nothing 
>> to do with the FAIL. ]
>> 
>> I've added an assert in rl_echo_signal_char and managed to trigger it to 
>> generate a core file corresponding to the FAIL condition (more details 
>> in the PR).
>> 
>> My guess at what happens is the following:
>> - we send a W to gdb
>> - readline handles this, and echoes it
>> - after readline echoing it, expect notices this and we send a ^C to gdb
>> - at this point readline is still in the code handling the W, and
>>    handles the ^C by echoing it.
>> 
>> Usually, at this point we're already back in gdb and handle the ^C 
>> without echoing it.
>> 
>
> Andrew, any comment?

Sorry, lost track of this thread.  Will take a look today.

Thanks,
Andrew

>
> Thanks,
> - Tom
>
>> Thanks,
>> - Tom
>> 
>>> Thanks,
>>> Andrew
>>>
>>>>
>>>> Tested on x86_64-linux.
>>>>
>>>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30458
>>>> ---
>>>>   gdb/testsuite/gdb.tui/wrap-line.exp | 6 ++++--
>>>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/gdb/testsuite/gdb.tui/wrap-line.exp 
>>>> b/gdb/testsuite/gdb.tui/wrap-line.exp
>>>> index 4587517504c..2bfe342e04d 100644
>>>> --- a/gdb/testsuite/gdb.tui/wrap-line.exp
>>>> +++ b/gdb/testsuite/gdb.tui/wrap-line.exp
>>>> @@ -25,6 +25,8 @@ set cols 50
>>>>   set lines 24
>>>>   set dims [list $lines $cols]
>>>> +set re_control_c "(\\^C)?Quit"
>>>> +
>>>>   # Fill line, assuming we start after the gdb prompt.
>>>>   proc fill_line { width } {
>>>>       set res ""
>>>> @@ -47,7 +49,7 @@ proc fill_line { width } {
>>>>   proc test_wrap { wrap_width } {
>>>>       # Generate a prompt and parse it.
>>>>       send_gdb "\003"
>>>> -    gdb_assert { [Term::wait_for "(^|$::gdb_prompt )Quit"] } "start 
>>>> line"
>>>> +    gdb_assert { [Term::wait_for "(^|$::gdb_prompt 
>>>> )$::re_control_c"] } "start line"
>>>>       # Fill the line to just before wrapping.
>>>>       set str [fill_line $wrap_width]
>>>> @@ -64,7 +66,7 @@ proc test_wrap { wrap_width } {
>>>>       # Generate a prompt and parse it.
>>>>       send_gdb "\003"
>>>> -    gdb_assert { [Term::wait_for "^WQuit"] } "prompt after wrap"
>>>> +    gdb_assert { [Term::wait_for "^W$::re_control_c"] } "prompt 
>>>> after wrap"
>>>>   }
>>>>   # Test wrapping in both CLI and TUI.
>>>>
>>>> base-commit: 0cc8cc5e6f82b8d3d8e3803c6f7f5e63f0c866ad
>>>> -- 
>>>> 2.35.3
>>>
>>