[llvm-dev] [RFC] Updating googletest to non-release tagged version

Tue Mar 20 05:52:04 PDT 2018

On 19 March 2018 at 19:56, Chandler Carruth <chandlerc at gmail.com> wrote:

> On Thu, Mar 15, 2018 at 11:10 AM David Blaikie via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> +Chandler who might have some thoughts on this.
>>
>
> FWIW, I have no concerns about updating to a modern googletest. More
> modern the better IMO if someone is willing to do the work to make sure it
> works on all our platforms, etc.
>

I'd be happy to do some of the work of this, and testing using MSVC14,
perhaps 15 too, on x86_64 Windows 10 and (fairly elderly) GCC, possibly
clang too, and Ubuntu 14.04, but I don't have easy access to other
platforms/toolchains etc, so I'd need some assistance for this.

>
> However:
>
>> Could you provide an example here of the motivation for the feature
>> you're missing?
>>
>
> I definitely think that the whole space of combinatorial testing should be
> carefully discussed. Seems like a high risk of long-running tests w/o
> providing much incremental value.
>

These are fair comments, and probably should be judged on a case-by-case
basis.

In my particular case from https://reviews.llvm.org/D44560, I currently
test the following 3 different cases across the full set of DWARF versions
and formats:
  - Parsing a valid line table
  - Emitting an error if the stated prologue length is greater than the
actual length
  - Emitting an error if the stated prologue length is shorter than the
actual length

The first is just testing the positive cases for each possible input. I
guess a single test for DWARF64 could be written for versions 2-4 and
another for version 5 (where there is more stuff between the two length
fields so this becomes interesting), similarly for DWARF32. To summarise, I
think that these cases are interesting: V5 + 32, V5 + 64, V2 + 32/64, V3 +
32/64, V4 + 32/64. The biggest issue I have with cutting down to just this
set is that it makes the tests less specific, e.g. at a glance, what is
important about the test - the fact that it is v4, or DWARF64, or both
independently, or the combination?

Related aside: I've realised since earlier that there is scope for version
2 tests, distinct from version 3: v2 tests test the lower boundary on valid
versions, and v3 the upper boundary on versions without
maximum_operations_per_instruction.

The latter two test cases are important because a) the length field has a
different size for DWARF32/64 and therefore the prologue length needs to be
measured from a different point between the different formats, and b) the
contents of the prologue are different in each of version 3, 4, and 5, and
thus the amount read will be different. We could test each individual
version, independently of the format, but it is theoretically possible for
an error to sneak in whereby the two different failure points cancel each
other out. The benefit is admittedly small, but these tests are fast, so I
don't think it hurts to have them.

James

>
>
>> Might help motivate the discussion (and/or we'll end up nitpicking how it
>> could be done differently without that feature... - which is sort of where
>> I'm going with this. Combinatorial test case expansion does seem a bit
>> suspicious to me - I'd hope we could pick a few examples from the various
>> equivalence classes & that would suffice?)
>>
>>
>> On Mon, Mar 12, 2018 at 9:01 AM James Henderson via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Hi all,
>>>
>>> I'm currently writing some unit tests for some debug line error handling
>>> code I'm working on (see e.g. https://reviews.llvm.org/D44382), and I
>>> just ran into an annoying disabled feature in gtest, specifically the
>>> "Combine" feature for use in combinatorially generating parameterised
>>> tests. A FIXME comment in ProfileData\CoverageMappingTest.cpp suggests
>>> that I'm not the only one to have tried and discovered that they cannot use
>>> this feature. The problem is that the version of googletest (v 1.8.0,
>>> released in Aug 2016) in the LLVM tree requires TR1 tuple support for this
>>> feature, which is not really supported in recent compilers, and has been
>>> explicitly disabled in our googletest CMakeLists.txt, thus disabling
>>> "Combine".
>>>
>>> I did a bit of looking around, and v 1.8.0 is indeed the last officially
>>> tagged release of googletest. However, there has been a lot of development
>>> on the framework since that point, including a fix to enable use of Combine
>>> with std::tuple-supporting compilers. There have been a number of issue
>>> raised on the googletest issue tracker (see e.g.
>>> https://github.com/google/googletest/issues/1467 or
>>> https://github.com/google/googletest/issues/1079) asking about a 1.9.0
>>> release, and there has been zero response from anybody answering the query
>>> of when/if it will happen. In the meantime, the last release gets older and
>>> crustier...
>>>
>>> I'd therefore like to propose something that might be seen as slightly
>>> controversial: update to use ToT googletest (or at least some reasonably
>>> recent version of master), at least until a new release is created.
>>>
>>> Thoughts?
>>>
>>> James
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
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>
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