Re: [PATCH v3 01/14] gdb/testsuite: introduce gdb_step_until_regexp

[Andrew Burgess <aburgess@redhat.com>]

Bruno Larsen via Gdb-patches <gdb-patches@sourceware.org> writes:

> Hi Andrew,
>
> thanks for the review!
>
> On 5/27/22 13:19, Andrew Burgess wrote:
>> Bruno Larsen via Gdb-patches <gdb-patches@sourceware.org> writes:
>> 
>>> Currently, GDB's testsuite uses a set amount of step commands to exit
>>> functions. This is a problem if a compiler emits different epilogue
>>> information from gcc, or emits no epilogue information at all. It was
>>> most noticeable if Clang was used to test GDB.
>>>
>>> To fix this unreliability, this commit introduces a new proc that will
>>> single step the inferior until it is stopped at a line that matches the
>>> given regexp, or until it steps too many times - defined as an optional
>>> argument. If the line is found, it shows up as a single PASS in the
>>> test, and if the line is not found, a single FAIL is emitted.
>>>
>>> This patch only introduces this proc, but does not add it to any
>>> existing tests, these will be introduced in the following commit.
>>> ---
>>>
>>> No change in v3
>>>
>>> New patch in v2
>>>
>>> ---
>>>   gdb/testsuite/lib/gdb.exp | 30 ++++++++++++++++++++++++++++++
>>>   1 file changed, 30 insertions(+)
>>>
>>> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
>>> index b04fbb89e4e..c0ca1d04cc2 100644
>>> --- a/gdb/testsuite/lib/gdb.exp
>>> +++ b/gdb/testsuite/lib/gdb.exp
>>> @@ -8648,5 +8648,35 @@ proc get_set_option_choices {set_cmd} {
>>>       return $values
>>>   }
>>>   
>>> +# This proc is used mainly to exit function in a compiler agnostic way
>>> +# It makes gdb single step and evaluate the output at every step, to see
>>> +# if the regexp is present.
>>> +#
>>> +# The proc takes 2 optional arguments, the first being the name of the
>>> +# test and the second the maximum amount of iterations until we expect to
>>> +# see the function. The default is 10 steps, since this is meant as the
>>> +# last step by default, and we don't expect any compiler generated epilogue
>>> +# longer than 10 steps.
>> 
>> I feel like you are being overly prescriptive in how this function
>> should be used.
>> 
>> I would rewrite this to just describe what the function does, and let
>> folk use it as they see fit.  Sure, initially it will only be used as
>> you imagine - that's why you're adding it.  But once it's there, who
>> knows what uses it might be put too.
>> 
>> I'd go with something like:
>> 
>>    # Single step until the pattern REGEXP is found.  Step at most
>>    # MAX_STEPS times, but stop stepping once REGEXP is found.
>>    #
>>    # If REGEXP is found then a single pass is emitted, otherwise, after
>>    # MAX_STEPS steps, a single fail is emitted.
>>    #
>>    # TEST_NAME is the name used in the pass/fail calls.
>> 
>
> Good point. I've used your version of the comment.
>
>>> +
>>> +proc gdb_step_until_regexp { regexp {test_name "single stepping until regexp"} {max_steps 10} } {
>> 
>> You should keep this line under 80 characters.  You can wrap the
>> arguments I believe, like:
>> 
>>    proc gdb_step_until_regexp { regexp
>>                                 {test_name "single stepping until regexp"}
>>                                 {max_steps 10} } {
>> 
>> However, I'd be tempted to take a different approach, like this:
>> 
>>    proc gdb_step_until_regexp { regexp {test_name ""} {max_steps 10} } {
>> 
>>      if { $test_name == "" } {
>>        set test_name "single stepping until regexp"
>>      }
>> 
>> The benefit I see in this approach is that if a user wants to adjust
>> max_steps, but doesn't care about the test name, they can do this:
>> 
>>    gdb_step_until_regexp "SOME_PATTERN" "" 50
>> 
>> And still get the default test name.
>
> That's a good reason. I didn't have any for my choice other than it's what I was comfortable with. Using your version again
>
>> 
>>> +    global gdb_prompt
>> 
>> I think this is OK, there's certainly lots of precedent for this
>> approach, but I think more often these days, we just refer to the global
>> directly as:
>> 
>>    $::gdb_prompt
>> 
>> As this removes the need for the 'global gdb_prompt' line.
>> 
>> But I don't think this is a hard requirement if you prefer what you
>> have.
>
> I do like this version more too, more clear that it is a global variable for new contributors.
>
> At this point, I wonder if I should add a co-authored tag to the
> patch.

That's up to you, but not required from my side.

Thanks,
Andrew

>
>> 
>> Thanks,
>> Andrew
>> 
>>> +
>>> +    set count 0
>>> +    gdb_test_multiple "step" "$test_name" {
>>> +	-re "$regexp\r\n$gdb_prompt $" {
>>> +	    pass $test_name
>>> +	}
>>> +	-re ".*$gdb_prompt $" {
>>> +	    if {$count < $max_steps} {
>>> +		incr count
>>> +		send_gdb "step\n"
>>> +		exp_continue
>>> +	    } else {
>>> +		fail $test_name
>>> +	    }
>>> +	}
>>> +    }
>>> +}
>>> +
>>>   # Always load compatibility stuff.
>>>   load_lib future.exp
>>> -- 
>>> 2.31.1
>> 
> Cheers!
> Bruno Larsen