[PATCH] Add a 'no-asserts' requirement option to LIT.

[David Blaikie]

On Tue, Feb 3, 2015 at 1:17 PM, Mehdi Amini <mehdi.amini at apple.com> wrote:

>
> On Feb 3, 2015, at 12:32 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>
>
> On Tue, Feb 3, 2015 at 12:19 PM, Mehdi Amini <mehdi.amini at apple.com>
> wrote:
>
>> Hi David,
>>
>> On Feb 3, 2015, at 11:15 AM, David Blaikie <dblaikie at gmail.com> wrote:
>> On Tue, Feb 3, 2015 at 11:03 AM, Owen Anderson <resistor at mac.com> wrote:
>>
>>> Hi chandlerc, joker.eph,
>>>
>>> This is useful when checking diagnostics and annotations that are only
>>> enabled in asserts mode.
>>
>>
>> Not sure I quite follow - "REQUIRES: Asserts" would be used for any test
>> case that's verifying a failure that's only enabled in asserts mode.
>> "REQUIRES: no-asserts" would be for testing the absence of that same
>> failure in a no-asserts build?
>>
>> That seems like a thing I wouldn't want to test for. The idea is that the
>> program has undefined behavior if it would assert but you're in a
>> non-asserts build. That's not a thing to test for - there's no
>> specific/guaranteed behavior in that case.
>>
>>
>> To provide you with more context: I am expecting some optional metadata
>> from the front-end, but in case they are malformed for any reason I want to
>> be bullet proof and handle this case gracefully (i.e. undefined behavior /
>> crashing is not acceptable). So I’d like my assert build to verify the
>> validity of the metadata but my release build to ignore it and set a
>> suitable default value that I know allows recovery most of the time.
>>
>> I can’t add a test to check if we recover correctly from an invalid
>> metadata without this.
>>
>> This is valid in general for the category of assertions we put to enforce
>> some invariant/properties that are important for optimization purposes but
>> does not prevent us from generating a correct code if they are broken.
>>
>> Does it make sense?
>>
>
> Not sure how everyone else feels, but I'd rather classify something like
> that that has well-defined recovery semantics, as something other than
> 'validity’.
>
>
> To be sure I understand correctly: do you mean an assertions is not
> welcome on the normal path if we have a well-defined recovery path?
>

That's my opinion: Failure to satisfy assertions implies UB and cannot be
tested for or verified in any way. Any assertion failure represents an
invariant in the program. If that's not the case then it's defined behavior
we should be always testing for. Otherwise it seems too easy to introduce
failures in the expected graceful recovery path.

Not sure about other people, maybe the prevailing attitude is not
consistent with mine.


>
> Thanks,
>
> —
> Mehdi
>
>
>
> When/where/how do you expect invalid metadata to come into your system?
>
>
>>
>> Thanks.
>>
>> Mehdi
>>
>>
>>
>>
>>
>>> Today we can only test the positive case (when asserts are enabled) but
>>> not the negative case.
>>>
>>> REPOSITORY
>>>   rL LLVM
>>>
>>> http://reviews.llvm.org/D7383
>>>
>>> Files:
>>>   test/lit.cfg
>>>
>>> Index: test/lit.cfg
>>> ===================================================================
>>> --- test/lit.cfg
>>> +++ test/lit.cfg
>>> @@ -370,6 +370,8 @@
>>>
>>>  if re.search(r'ON', llvm_config_cmd.stdout.read().decode('ascii')):
>>>      config.available_features.add('asserts')
>>> +else:
>>> +    config.available_features.add('no-asserts')
>>>  llvm_config_cmd.wait()
>>>
>>>  if 'darwin' == sys.platform:
>>>
>>> EMAIL PREFERENCES
>>>   http://reviews.llvm.org/settings/panel/emailpreferences/
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>
>>
>>
>
>
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