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Marco Massenzio commented on MESOS-3141: ---------------------------------------- That's probably because RB assumes sane behavior :) This points to a larger issue (which I am not sure anyone ever looked into or is there even a Jira for?) that we should not store binaries/libraries inside Mesos repo (eg, protobuf; zookeeper; gmock; other stuff I forget now, I'm sure...) Before making this change, we should really ensure this doesn't cause build failures on *all* supported OSes (Ubuntu/CentOS/RHEL) or we'll only find out at release time, and that will be really A Bad Thing. I'm all for upgrading gmock, but let's please proceed carefully here. > Compiler warning when mocking function type has an enum return type. > -------------------------------------------------------------------- > > Key: MESOS-3141 > URL: https://issues.apache.org/jira/browse/MESOS-3141 > Project: Mesos > Issue Type: Bug > Affects Versions: 0.23.0 > Reporter: Michael Park > Assignee: haosdent > Labels: mesosphere > > The purpose of this ticket is to document a very cryptic error message > (actually a warning that gets propagated by {{-Werror}}) that gets generated > by {{clang-3.5}} from {{gmock}} source code when trying to mock a perfectly > innocent-looking function. > h3. Problem > The following code is attempting to mock a {{MesosExecutorDriver}}: > {code} > class MockMesosExecutorDriver : public MesosExecutorDriver { > public: > MockMesosExecutorDriver(mesos::Executor* executor) > : MesosExecutorDriver(executor) {} > MOCK_METHOD1(sendStatusUpdate, Status(const TaskStatus&)); > }; > {code} > The above code generates the following error message: > {noformat} > In file included from > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/gmock.h:58: > In file included from > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/gmock-actions.h:46: > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/internal/gmock-internal-utils.h:355:10: > error: indirection of non-volatile null pointer will be deleted, not trap > [-Werror,-Wnull-dereference] > return *static_cast<typename remove_reference<T>::type*>(__null); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/gmock-actions.h:78:22: > note: in instantiation of function template specialization > 'testing::internal::Invalid<mesos::Status>' requested here > return internal::Invalid<T>(); > ^ > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/gmock-actions.h:190:43: > note: in instantiation of member function > 'testing::internal::BuiltInDefaultValue<mesos::Status>::Get' requested here > internal::BuiltInDefaultValue<T>::Get() : *value_; > ^ > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/gmock-spec-builders.h:1435:34: > note: in instantiation of member function > 'testing::DefaultValue<mesos::Status>::Get' requested here > return DefaultValue<Result>::Get(); > ^ > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/gmock-spec-builders.h:1334:22: > note: in instantiation of member function > 'testing::internal::FunctionMockerBase<mesos::Status (const mesos::TaskStatus > &)>::PerformDefaultAction' requested here > func_mocker->PerformDefaultAction(args, call_description)); > ^ > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/gmock-spec-builders.h:1448:26: > note: in instantiation of function template specialization > 'testing::internal::ActionResultHolder<mesos::Status>::PerformDefaultAction<mesos::Status > (const mesos::TaskStatus &)>' requested here > return ResultHolder::PerformDefaultAction(this, args, call_description); > ^ > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/gmock-generated-function-mockers.h:81:7: > note: in instantiation of member function > 'testing::internal::FunctionMockerBase<mesos::Status (const mesos::TaskStatus > &)>::UntypedPerformDefaultAction' requested here > class FunctionMocker<R(A1)> : public > ^ > ../3rdparty/libprocess/3rdparty/gmock-1.6.0/include/gmock/internal/gmock-internal-utils.h:355:10: > note: consider using __builtin_trap() or qualifying pointer with 'volatile' > return *static_cast<typename remove_reference<T>::type*>(__null); > ^ > {noformat} > The source of the issue here is that {{Status}} is an {{enum}}. In > {{gmock-1.6.0/include/gmock/internal/gmock-internal-utils.h}} you can find > the following function: > {code} > template <typename T> > T Invalid() { > return *static_cast<typename remove_reference<T>::type*>(NULL); > } > {code} > This function gets called with the return type of a mocked function. In our > case, the return type of the mocked function is {{Status}}. > Attempting to compile the following minimal example with {{clang-3.5}} > reproduces the error message: > {code} > #include <type_traits> > template <typename T> > T invalid() { > return *static_cast<typename std::remove_reference<T>::type *>(nullptr); > } > enum E { A, B }; > int main() { > invalid<E>(); > } > {code} > * See it online on [GCC Explorer|https://goo.gl/t1FepZ] > Note that if the type is not an {{enum}}, the warning is not generated. This > is why existing mocked functions that return non-{{enum}} types such as > {{Future<void>}} does not encounter this issue. > h3. Solutions > The simplest solution is to add {{-Wno-null-deference}} to > {{mesos_tests_CPPFLAGS}} in {{src/Makefile.am}}. > {code} > mesos_tests_CPPFLAGS = $(MESOS_CPPFLAGS) -Wno-null-dereference > {code} > Another solution is to upgrade {{gmock}} from *1.6* to *1.7* to as I believe > this problem is solved in the newer versions. -- This message was sent by Atlassian JIRA (v6.3.4#6332)