Compiler problem with operator and include catch_all.hpp

[rsc-vitronic]

Description
There is a compiler error, when #include <catch2/catch_all.hpp> is included.

Error msg is: C2039: "value": is not an element of "Catch::Detail::is_eq_comparable<LhsT,std::_Vector_const_iterator<std::_Vector_val<std::_Simple_types<_Ty>>>,void>"

Simple example when the error occurs:

#include <catch2/catch_all.hpp>

TEST_CASE("first") {
  REQUIRE(true);
}

Using the include catch2/catch_test_macros.hpp instead of catch2/catch_all.hpp all is fine

Reproduction steps
Including catch2/catch_all.hpp in one of the catch internal tests (e.g. String.tests.cpp) reproduce this error too.

Platform information:

• OS: Windows 10
• Compiler+version: Visual Studio 2017 15.9.16
• SDK-Version: 10.0.17763.0
• Catch version: v3.5.0 and v3.5.1

Using v3.4.0 all is fine.

[rsc-vitronic]

The error can be reproduced,

#include <catch2/catch_test_macros.hpp>



#include <catch2/benchmark/catch_benchmark_all.hpp>
#include <catch2/catch_approx.hpp>
#include <catch2/catch_assertion_info.hpp>
#include <catch2/catch_assertion_result.hpp>
#include <catch2/catch_config.hpp>
#include <catch2/catch_get_random_seed.hpp>
#include <catch2/catch_message.hpp>
#include <catch2/catch_section_info.hpp>
#include <catch2/catch_session.hpp>
#include <catch2/catch_tag_alias.hpp>
#include <catch2/catch_tag_alias_autoregistrar.hpp>
#include <catch2/catch_template_test_macros.hpp>
#include <catch2/catch_test_case_info.hpp>
#include <catch2/catch_test_macros.hpp>
#include <catch2/catch_test_spec.hpp>
#include <catch2/catch_timer.hpp>
#include <catch2/catch_tostring.hpp>
#include <catch2/catch_totals.hpp>
#include <catch2/catch_translate_exception.hpp>
#include <catch2/catch_version.hpp>
#include <catch2/catch_version_macros.hpp>


// #include <catch2/generators/catch_generators_all.hpp>
#include <catch2/generators/catch_generator_exception.hpp>
#include <catch2/generators/catch_generators.hpp>
#include <catch2/generators/catch_generators_adapters.hpp>
// adding this include creates this error
#include <catch2/generators/catch_generators_random.hpp>
#include <catch2/generators/catch_generators_range.hpp>


TEST_CASE("first") {
	REQUIRE(true);
	//REQUIRE(5 <= 5);
}

In the combination of the above includes (as they are from catch_all) the error can be "tuned on / off" by include catch_generators_random.hpp

Catch version: v3.5.0

[ChrisThrasher]

Can you reproduce this with a newer version of Visual Studio or does it only appear with VS 2017?

[rsc-vitronic]

I'v just tried VS 2017 till now.

But with the new Catch version: v3.5.2 I've get the Error C2039 also in the SelfTest of
RandomNumberGeneration.tests.cpp

TEST_CASE("Comparison ops", "[rng]") {
    using Catch::SimplePcg32;
    REQUIRE(SimplePcg32{} == SimplePcg32{}); // C2039:  "value": is not an element of "Catch::Detail::is_eq_comparable<LhsT,Catch::SimplePcg32,void>"	SelfTest	...\14.16.27023\include\type_traits	74	

When I reduce the header include to the following in RandomNumberGeneration.tests.cpp and remove the rest of code, the Code compiles. Including catch_random_integer_helpers.hpp will create the error C2039:

#include <catch2/catch_test_macros.hpp>
#include <catch2/catch_template_test_macros.hpp>
#include <catch2/internal/catch_floating_point_helpers.hpp>
// #include <catch2/internal/catch_random_integer_helpers.hpp>
#include <catch2/internal/catch_random_number_generator.hpp>
// #include <catch2/internal/catch_random_seed_generation.hpp>
// #include <catch2/internal/catch_uniform_floating_point_distribution.hpp>
// #include <catch2/internal/catch_uniform_integer_distribution.hpp>
#include <catch2/generators/catch_generators.hpp>
#include <catch2/matchers/catch_matchers_range_equals.hpp>

TEST_CASE("Comparison ops", "[rng]") {
    using Catch::SimplePcg32;
    REQUIRE(SimplePcg32{} == SimplePcg32{});
    REQUIRE(SimplePcg32{ 0 } != SimplePcg32{});
    REQUIRE_FALSE(SimplePcg32{ 1 } == SimplePcg32{ 2 });
    REQUIRE_FALSE(SimplePcg32{ 1 } != SimplePcg32{ 1 });
}

Catch version: v3.5.2

[rsc-vitronic]

Can you reproduce this with a newer version of Visual Studio or does it only appear with VS 2017?

Verified with the SelfTest of Catch v3.5.2 - Checked with the other compiler Visual Studio locally:
Visual Studio 2019 (v142) SDK Version used 10.0.10240.0 - SUCCESS
Visual Studio 2022 (v143) SDK Version used 10.0.10240.0 - SUCCESS
Visual Studio 2017 (v141) SDK Version used 10.0.10240.0 - FAILED

The results for Visual Studio 2019 & Visual Studio 2022 where expected, since they are part of the Windows builds windows-simple-builds.yml.

Question is, why is Visual Studio 2017 v141 not part of this test-builds. Is Visual Studio 2017not official supported any more?

Catch version: v3.5.2

[horenmar]

2017 is currently not supported. The support policy is C++14 + maybe reasonable workarounds. Since I haven't used 2017 since, ..., well, ever, I am not interested in figuring out a workaround for VS2017 to accept the new RNG code.

If you are interested in figuring it out, I can point you to catch_random_integer_helpers.hpp, which trigger the bug.

[rsc-vitronic]

Hi horenmar,
thanks for your replay. I can understand that not all compilers with their peculiarities can be supported.
May be it would be helpfull to define the supported compiler on the main project page.

[rsc-vitronic]

In the meantime I was able to narrow down the problem further. The compiler stumbles with the == operator of a template structure.

#include <catch2/catch_test_macros.hpp>

namespace Catch {
    namespace Detail {
        template <typename T>
        struct MyTemplate {
            friend bool operator==( MyTemplate const& lhs,MyTemplate const& rhs ) { return false; }
        };
    } // namespace Detail
} // namespace Catch

namespace Catch {
    struct MyClass {
        friend bool operator==( MyClass const& lhs, MyClass const& rhs ) { return false; }
    };
} // namespace Catch

TEST_CASE( "first", "[x]" ) {
    Catch::Detail::MyTemplate<std::uint64_t> aa; // comment this line to get rid of the error
    CHECK_FALSE( std::string( "Hallo" ) == std::string( "huhu" ) );
    Catch::MyClass a, b;
    CHECK_FALSE( a == b ); // will generate compile error, when aa is defined
}

Then comes CATCH_INTERNAL_DEFINE_EXPRESSION_EQUALITY_OPERATOR( eq, == )
in stumble.
I couldn't solve the problem straight away. I'm not sure how to point the compiler in the right direction.

A simple but unpleasant solution is to put the template struct/class in its own namespace, such as Catch::Detail::Internal.

Puting all the code of the catch_random_integer_helpers.hpp in an inner namespace solved the problem and the code compiled and was usable. But I think that is not the desired strategy.

How about making the new RNG code deactivable using the CMAKE option? That would also mean Catch2 is usable with Visual Studio 2017.

[horenmar]

Actually it looks like making the operator not-friend is sufficient: https://godbolt.org/z/783xW6jT5

[horenmar]

(I would be willing to merge that PR)