failures with gtest 1.13+

[doronbehar]

At NixOS we are experiencing this error with our own gtest 1.14:

       > /build/source/googletest/googletest/include/gtest/gtest.h:302:41: error: expected '>' before '<' token
       >   302 |   template <typename T, std::enable_if_t<std::is_convertible<T, int64_t>::value,
       >       |                                         ^
       > make[3]: *** [tests/src/CMakeFiles/wpa2_decrypt_test.dir/build.make:76: tests/src/CMakeFiles/wpa2_decrypt_test.dir/wpa2_decrypt_test.cpp.o] Error 1
       > make[3]: Leaving directory '/build/source/build'
       > make[2]: *** [CMakeFiles/Makefile2:2383: tests/src/CMakeFiles/wpa2_decrypt_test.dir/all] Error 2
       > make[2]: Leaving directory '/build/source/build'
       > make[1]: *** [CMakeFiles/Makefile2:830: tests/src/CMakeFiles/tests.dir/rule] Error 2
       > make[1]: Leaving directory '/build/source/build'
       > make: *** [Makefile:439: tests] Error 2

We managed to fix the tests with this patch:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 902233e676ee..49ac8a1010a4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -103,17 +103,9 @@ ENDIF()
 # C++11 support
 OPTION(LIBTINS_ENABLE_CXX11 "Compile libtins with c++11 features" ON)
 IF(LIBTINS_ENABLE_CXX11)
-    # We only use declval and decltype on gcc/clang as VC fails to build that code,
-    # at least on VC2013
-    IF(HAS_CXX11_RVALUE_REFERENCES AND HAS_CXX11_FUNCTIONAL AND HAS_CXX11_CHRONO AND
-       HAS_CXX11_NOEXCEPT AND ((HAS_CXX11_DECLVAL AND HAS_CXX11_DECLTYPE) OR MSVC))
-        SET(TINS_HAVE_CXX11 ON)
-        MESSAGE(STATUS "Enabling C++11 features")
-        SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CXX11_COMPILER_FLAGS}")
-    ELSE()
-        MESSAGE(WARNING "The compiler doesn't support the necessary C++11 features. "
-                        "Disabling C++11 on this build")
-    ENDIF()
+    SET(TINS_HAVE_CXX11 ON)
+    MESSAGE(STATUS "Using C++11 features")
+    SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
 ELSE(LIBTINS_ENABLE_CXX11)
     MESSAGE(
         WARNING

But it's a bit hard coding. I'm not the downstream maintainer, so I might not have time to help you debug this on our end, but I'm ought to tell you.

[GiulioCocconi]

Maybe you could keep the check logic and call set_property(TARGET tests PROPERTY CXX_STANDARD 14) in tests/src/CMakeLists.txt. This way the library keeps using C++11 for the actual code and switches to C++14 only for gtests.