[c++] googletest tests fail on newer versions of googletest which dropped C++11 support

[yurivict]

Description

Failure message:

In file included from /usr/ports/misc/lightgbm/work/LightGBM-4.0.0/tests/cpp_tests/test_main.cpp:5:
In file included from /usr/local/include/gtest/gtest.h:64:
In file included from /usr/local/include/gtest/gtest-assertion-result.h:46:
In file included from /usr/local/include/gtest/gtest-message.h:57:
/usr/local/include/gtest/internal/gtest-port.h:270:2: error: C++ versions less than C++14 are not supported.
#error C++ versions less than C++14 are not supported.
 ^
In file included from /usr/ports/misc/lightgbm/work/LightGBM-4.0.0/tests/cpp_tests/test_main.cpp:5:
In file included from /usr/local/include/gtest/gtest.h:65:
In file included from /usr/local/include/gtest/gtest-death-test.h:43:
In file included from /usr/local/include/gtest/internal/gtest-death-test-internal.h:47:
In file included from /usr/local/include/gtest/gtest-matchers.h:48:
In file included from /usr/local/include/gtest/gtest-printers.h:115:
/usr/local/include/gtest/internal/gtest-internal.h:636:54: error: too few template arguments for class template 'less'
  typedef ::std::map<std::string, CodeLocation, std::less<>> RegisteredTestsMap;
                                                     ^
/usr/include/c++/v1/__functional/operations.h:366:29: note: template is declared here
struct _LIBCPP_TEMPLATE_VIS less
                            ^
In file included from /usr/ports/misc/lightgbm/work/LightGBM-4.0.0/tests/cpp_tests/test_main.cpp:5:
In file included from /usr/local/include/gtest/gtest.h:65:
In file included from /usr/local/include/gtest/gtest-death-test.h:43:
In file included from /usr/local/include/gtest/internal/gtest-death-test-internal.h:47:
In file included from /usr/local/include/gtest/gtest-matchers.h:48:
In file included from /usr/local/include/gtest/gtest-printers.h:115:
/usr/local/include/gtest/internal/gtest-internal.h:613:22: error: member reference base type 'testing::internal::TypedTestSuitePState::RegisteredTestsMap' (aka 'int') is not a structure or union
    registered_tests_.insert(
    ~~~~~~~~~~~~~~~~~^~~~~~~
/usr/local/include/gtest/internal/gtest-internal.h:619:29: error: member reference base type 'const testing::internal::TypedTestSuitePState::RegisteredTestsMap' (aka 'const int') is not a structure or union
    return registered_tests_.count(test_name) > 0;
           ~~~~~~~~~~~~~~~~~^~~~~~
/usr/local/include/gtest/internal/gtest-internal.h:623:5: error: 'testing::internal::TypedTestSuitePState::RegisteredTestsMap' (aka 'int') is not a class, namespace, or enumeration
    RegisteredTestsMap::const_iterator it = registered_tests_.find(test_name);
    ^
/usr/local/include/gtest/internal/gtest-internal.h:623:62: error: member reference base type 'const testing::internal::TypedTestSuitePState::RegisteredTestsMap' (aka 'const int') is not a structure or union
    RegisteredTestsMap::const_iterator it = registered_tests_.find(test_name);
                                            ~~~~~~~~~~~~~~~~~^~~~~
/usr/local/include/gtest/internal/gtest-internal.h:624:41: error: member reference base type 'const testing::internal::TypedTestSuitePState::RegisteredTestsMap' (aka 'const int') is not a structure or union
    GTEST_CHECK_(it != registered_tests_.end());
                       ~~~~~~~~~~~~~~~~~^~~~
/usr/local/include/gtest/internal/gtest-port.h:1027:35: note: expanded from macro 'GTEST_CHECK_'
  if (::testing::internal::IsTrue(condition)) \
                                  ^~~~~~~~~
7 errors generated.

Environment info

LightGBM version or commit hash: 4.0.0
clang-15
pytest-7.3.1
FreeBSD 13.2

[jameslamb]

Thanks for using LightGBM.

Please provide the exact commands you ran which produced this error message. With just an error message, it's difficult for us to help you.

[yurivict]

Complete log is here.

[jameslamb]

Can you explain the context of what this build is? It looks quite complicated.

For example, what are these patches?

===>  Patching for lightgbm-4.0.0
===>  Applying FreeBSD patches for lightgbm-4.0.0 from /usr/ports/misc/lightgbm/files

We'd very much appreciate if you could reduce this report to a minimal one that reproduces the problem you're facing.

[yurivict]

This is a FreeBSD port build.
The patch applied is:

--- CMakeLists.txt.orig 2022-12-29 04:59:34 UTC
+++ CMakeLists.txt
@@ -507,7 +507,7 @@ endif(__BUILD_FOR_R)
 
 #-- Google C++ tests
 if(BUILD_CPP_TEST)
-  find_package(GTest CONFIG)
+  find_package(GTest)
   if(NOT GTEST_FOUND)
     message(STATUS "Did not find Google Test in the system root. Fetching Google Test now...")
     include(FetchContent)

It shouldn't matter for this issue.

The core problem is that googletest no longer supports c++11, and the project uses c++11. You should change that to c++20, for example.

[jameslamb]

Interesting! I guess we haven't experienced that in this project's CI because we don't preinstall googletest, and instead rely on CMake to pull in a specific, fairly-old version.

LightGBM/CMakeLists.txt

Lines 607 to 617 in d73c6b5

	if(NOT GTEST_FOUND)
	message(STATUS "Did not find Google Test in the system root. Fetching Google Test now...")
	include(FetchContent)
	FetchContent_Declare(
	googletest
	GIT_REPOSITORY https://github.com/google/googletest.git
	GIT_TAG release-1.11.0
	)
	FetchContent_MakeAvailable(googletest)
	add_library(GTest::GTest ALIAS gtest)
	endif()

That version of googletest still supported C++11. That support was dropped in v1.12.1 (June 30, 2022.

You should change that to c++20, for example.

I absolutely don't support dropping C++11, C++14, and C++17 support yet in LightGBM. That would impact a lot of the project's users, and so far we haven't found that maintaining such compatibility has been a major issue. There is some discussion in #5691 if you're curious.

However... I'd definitely support upgrading to the latest release of googletest and using the C++20 standard when running those tests. That'd give us some minimal test coverage on C++20 (we currently have none) and make it easier for repackagers like you.

I'll put up a PR for that shortly, thanks for the report and sorry for the inconvenience.

[github-actions]

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