feat(Core): Enable C++20 support (#10440)

* feat(Core): Enable C++20 support

* Update Duration.h

* Revert "Update Duration.h"

This reverts commit 177093e992c5d47d8c3b978c84857f5ecba12889.

* maybe fix GCC

* cherry-pick https://gcc.gnu.org/pipermail/gcc-cvs/2020-June/299715.html

* Update Duration.h

* Update Duration.h

* Update Duration.h

* Update Duration.h

* Update Duration.h

* Update Duration.h

* Update Duration.h

* Revert "Update Duration.h"

This reverts commit dc4e2ce281dd1a33cfac5be56488a3b96131bfd5.

* Update Duration.h

* Update Duration.h

* Update Duration.h

* cleanup

* more cleanup

* maybe fix build

* restore advstd::type_identity because GCC8 is garbage

* Update advstd.h

* fix gcc8 💤

* Update CMakeLists.txt

* Update CMakeLists.txt

* Update src/common/Utilities/advstd.h

Co-authored-by: Francesco Borzì <borzifrancesco@gmail.com>

src/cmake/macros/ConfigureBaseTargets.cmake

@@ -16,15 +16,9 @@ add_library(acore-compile-option-interface INTERFACE)
 # Use -std=c++11 instead of -std=gnu++11
 set(CXX_EXTENSIONS OFF)
 
-if (USE_CPP_20)
-  # Enable support С++20
-  set(CMAKE_CXX_STANDARD 20)
-  message(STATUS "Enabled С++20 standard")
-else()
-  # Enable support С++17
-  set(CMAKE_CXX_STANDARD 17)
-  message(STATUS "Enabled С++17 standard")
-endif()
+# Enable C++20 support
+set(CMAKE_CXX_STANDARD 20)
+message(STATUS "Enabled С++20 standard")
 
 # An interface library to make the warnings level available to other targets
 # This interface taget is set-up through the platform specific script

src/cmake/showoptions.cmake

@@ -182,12 +182,6 @@ if(BUILD_SHARED_LIBS)
   WarnAboutSpacesInBuildPath()
 endif()
 
-if (USE_CPP_20)
-  message("")
-  message(" *** Enabled C++20 standart")
-  message(" *** Please note that this is an experimental feature!")
-endif()
-
 if (CONFIG_ABORT_INCORRECT_OPTIONS)
   message("")
   message(" WARNING !")

src/common/Utilities/Duration.h

@@ -35,7 +35,22 @@ using Minutes = std::chrono::minutes;
 /// Hours shorthand typedef.
 using Hours = std::chrono::hours;
 
-#if __cplusplus > 201703L
+// Workaround for GCC and Clang 10 in C++20
+#if defined(__GNUC__) && (!defined(__clang__) || (__clang_major__ == 10))
+/// Days shorthand typedef.
+using Days = std::chrono::duration<__INT64_TYPE__, std::ratio<86400>>;
+
+/// Weeks shorthand typedef.
+using Weeks = std::chrono::duration<__INT64_TYPE__, std::ratio<604800>>;
+
+/// Years shorthand typedef.
+using Years = std::chrono::duration<__INT64_TYPE__, std::ratio<31556952>>;
+
+/// Months shorthand typedef.
+using Months = std::chrono::duration<__INT64_TYPE__, std::ratio<2629746>>;
+
+#else
+
 /// Days shorthand typedef.
 using Days = std::chrono::days;
 
@@ -47,19 +62,8 @@ using Years = std::chrono::years;
 
 /// Months shorthand typedef.
 using Months = std::chrono::months;
-#else
-/// Days shorthand typedef. (delete after start support c++20)
-using Days = std::chrono::duration<int, std::ratio_multiply<std::ratio<24>, Hours::period>>;
 
-/// Weeks shorthand typedef. (delete after start support c++20)
-using Weeks = std::chrono::duration<int, std::ratio_multiply<std::ratio<7>, Days::period>>;
-
-/// Years shorthand typedef. (delete after start support c++20)
-using Years = std::chrono::duration<int, std::ratio_multiply<std::ratio<146097, 400>, Days::period>>;
-
-/// Months shorthand typedef. (delete after start support c++20)
-using Months = std::chrono::duration<int, std::ratio_divide<Years::period, std::ratio<12>>>;
-#endif
+#endif // GCC_VERSION
 
 /// time_point shorthand typedefs
 using TimePoint = std::chrono::steady_clock::time_point;

src/common/Utilities/EventProcessor.h

@@ -21,7 +21,6 @@
 #include "Define.h"
 #include "Duration.h"
 #include "Random.h"
-
 #include "advstd.h"
 #include <map>
 #include <type_traits>

src/common/Utilities/advstd.h

@@ -24,6 +24,8 @@
 // this namespace holds implementations of upcoming stdlib features that our c++ version doesn't have yet
 namespace advstd
 {
+    // This workaround for std::remove_cvref_t, std::type_identify is needed for GCC 8...
+    // TODO: remove when we drop GCC 8 support. https://en.cppreference.com/w/cpp/compiler_support/20
     // C++20 advstd::remove_cvref_t
     template <class T>
     using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<T>>;

src/server/game/Chat/Hyperlinks.cpp

@@ -24,7 +24,6 @@
 #include "SharedDefines.h"
 #include "SpellInfo.h"
 #include "SpellMgr.h"
-#include "advstd.h"
 
 using namespace Acore::Hyperlinks;