C++ gmock 在命名空间中找不到方法参数的 operator==

Question

我无法使用 gcc 6.4 编译以下代码。
gmock 版本是 1.8.1。
也许 operator== 这里看起来很奇怪，但由于它的大小，我无法附上完整的代码。

#include <iostream>
#include <gmock/gmock.h>

template<class T>
constexpr bool operator==(T&&, T&&) noexcept
{
    return true;
}

namespace NNNN
{

struct Param2
{
    int i;
};

} // namespace NN

using ::testing::_;
using ::testing::Return;
using ::testing::AtMost;


struct Param
{
    int i;
};

struct A
{
    MOCK_METHOD1(f, int(const Param&));
};

struct B
{
    MOCK_METHOD1(f, int(const NNNN::Param2&));
};


TEST(Test, test)
{
    A a;
    EXPECT_CALL(a, f(Param{ 1 }));

    B b;
    std::cout << (NNNN::Param2{ 1 } == NNNN::Param2{ 2 }) << std::endl;
    EXPECT_CALL(b, f(NNNN::Param2{ 1 }));
}

int main(int argc, char** argv)
{
    ::testing::InitGoogleMock(&argc, argv);
    return RUN_ALL_TESTS();
}

我得到的错误:

In file included from /usr/local/lib/googletest/1.8.1/lib/pkgconfig/../../include/gmock/gmock-spec-builders.h:71:0,
                 from /usr/local/lib/googletest/1.8.1/lib/pkgconfig/../../include/gmock/gmock-generated-function-mockers.h:44,
                 from /usr/local/lib/googletest/1.8.1/lib/pkgconfig/../../include/gmock/gmock.h:62,
                 from /home/jzldfb/projects/uc_workspace/ultracruise/rte/utils/configuration/daemon/sub_module/test/TestApi2.cpp:7:
/usr/local/lib/googletest/1.8.1/lib/pkgconfig/../../include/gmock/gmock-matchers.h: In instantiation of 'bool testing::internal::AnyEq::operator()(const A&, const B&) const [with A = NNNN::Param2; B = NNNN::Param2]':
/usr/local/lib/googletest/1.8.1/lib/pkgconfig/../../include/gmock/gmock-matchers.h:1083:18:   required from 'bool testing::internal::ComparisonBase<D, Rhs, Op>::Impl<Lhs>::MatchAndExplain(Lhs, testing::MatchResultListener*) const [with Lhs = const NNNN::Param2&; D = testing::internal::EqMatcher<NNNN::Param2>; Rhs = NNNN::Param2; Op = testing::internal::AnyEq]'
/home/jzldfb/projects/uc_workspace/ultracruise/rte/utils/configuration/daemon/sub_module/test/TestApi2.cpp:60:1:   required from here
/usr/local/lib/googletest/1.8.1/lib/pkgconfig/../../include/gmock/gmock-matchers.h:238:60: error: no match for 'operator==' (operand types are 'const NNNN::Param2' and 'const NNNN::Param2')
   bool operator()(const A& a, const B& b) const { return a == b; }

如果我删除 NNNN 命名空间，则编译成功。
如果我为在其 operator== 中调用模板 operator== 的 Param2 添加模板包装器，则编译成功。

Answer 1

感谢您将我发送到 ADL 页面。
解决方法是添加:

namespace testing {
namespace internal {
    using ::operator==;
} }

testing::internal 它是 gmock 中的一个命名空间，其中 operator== 被调用。
上面的代码指示此命名空间在全局命名空间中查找 operator==。