Restore observation of the value of CMAKE_CXX_STANDARD when

determining which C++ standard to use.

Author: ned14

CMakeLists.txt

@@ -16,8 +16,16 @@ ensure_git_subrepo("${CMAKE_CURRENT_SOURCE_DIR}/include/quickcpplib/byte/include
 # Sets the usual PROJECT_NAME etc
 project(quickcpplib VERSION 0.1.0.0 LANGUAGES C CXX)
 include(CMakeDependentOption)
-option(QUICKCPPLIB_REQUIRE_CXX20 "Add cxx20 compile feature to the target which in turn makes byte-lite, span-lite and akrzemi1/Optional optional." OFF)
-cmake_dependent_option(QUICKCPPLIB_REQUIRE_CXX17 "Add cxx17 compile feature to the target which in turn makes akrzemi1/Optional optional." OFF "NOT QUICKCPPLIB_REQUIRE_CXX20" ON)
+set(CMAKE_CXX_STANDARD_IS_GREATER_EQUAL_17 FALSE)
+set(CMAKE_CXX_STANDARD_IS_GREATER_EQUAL_20 FALSE)
+if(CMAKE_CXX_STANDARD GREATER_EQUAL 20)
+  set(CMAKE_CXX_STANDARD_IS_GREATER_EQUAL_20 TRUE)
+  set(CMAKE_CXX_STANDARD_IS_GREATER_EQUAL_17 TRUE)
+elseif(CMAKE_CXX_STANDARD GREATER_EQUAL 17)
+  set(CMAKE_CXX_STANDARD_IS_GREATER_EQUAL_17 TRUE)
+endif()
+cmake_dependent_option(QUICKCPPLIB_REQUIRE_CXX20 "Add cxx20 compile feature to the target which in turn makes byte-lite, span-lite and akrzemi1/Optional optional." OFF "NOT CMAKE_CXX_STANDARD_IS_GREATER_EQUAL_20" ON)
+cmake_dependent_option(QUICKCPPLIB_REQUIRE_CXX17 "Add cxx17 compile feature to the target which in turn makes akrzemi1/Optional optional." OFF "NOT CMAKE_CXX_STANDARD_IS_GREATER_EQUAL_17" ON)
 cmake_dependent_option(QUICKCPPLIB_USE_SYSTEM_BYTE_LITE "Whether to use embedded nonstd::byte-lite. Used by various package managers such as vcpkg." OFF "NOT QUICKCPPLIB_REQUIRE_CXX17" OFF)
 cmake_dependent_option(QUICKCPPLIB_USE_SYSTEM_SPAN_LITE "Whether to use embedded nonstd::span-lite. Used by various package managers such as vcpkg." OFF "NOT QUICKCPPLIB_REQUIRE_CXX20" OFF)
 # quickcpplib does not provide a master header file

include/quickcpplib/optional.hpp

@@ -27,8 +27,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 #include "config.hpp"
 
+#include "cpp_feature.h"
+
 #if !defined(QUICKCPPLIB_USE_STD_OPTIONAL)
-#if _HAS_CXX17 || (__cplusplus >= 201700 && (!defined(__APPLE__) || _LIBCPP_VERSION > 7000 /* approx end of 2017 */))
+#if _HAS_CXX17 ||                                                                                                      \
+(__cplusplus >= 201700 && (!defined(__APPLE__) || _LIBCPP_VERSION > 7000 /* approx end of 2017 */)) ||                 \
+!defined(__cpp_exceptions)
 #define QUICKCPPLIB_USE_STD_OPTIONAL 1
 #else
 #define QUICKCPPLIB_USE_STD_OPTIONAL 0
@@ -48,7 +52,12 @@ namespace optional
 
 QUICKCPPLIB_NAMESPACE_END
 
-#else // ^^^ QUICKCPPLIB_USE_STD_OPTIONAL / not QUICKCPPLIB_USE_STD_OPTIONAL vvv
+#else  // ^^^ QUICKCPPLIB_USE_STD_OPTIONAL / not QUICKCPPLIB_USE_STD_OPTIONAL vvv
+
+#if !defined(__cpp_exceptions)
+#error                                                                                                                 \
+"Our <optional> polyfill requires C++ exceptions globally enabled. Try increasing C++ standard to 2017 or higher to enable std <optional>"
+#endif
 
 #ifdef _MSC_VER
 #pragma warning(push)
@@ -68,6 +77,6 @@ namespace optional
 
 QUICKCPPLIB_NAMESPACE_END
 
-#endif // ^^^ not QUICKCPPLIB_USE_STD_OPTIONAL ^^^
+#endif  // ^^^ not QUICKCPPLIB_USE_STD_OPTIONAL ^^^
 
 #endif

include/quickcpplib/revision.hpp

@@ -1,4 +1,4 @@
 // Note the second line of this file must ALWAYS be the git SHA, third line ALWAYS the git SHA update time
-#define QUICKCPPLIB_PREVIOUS_COMMIT_REF    7d002f5eba98df28c81678d1341055f5792f4d7d
-#define QUICKCPPLIB_PREVIOUS_COMMIT_DATE   "2025-02-02 18:35:50 +00:00"
-#define QUICKCPPLIB_PREVIOUS_COMMIT_UNIQUE 7d002f5e
+#define QUICKCPPLIB_PREVIOUS_COMMIT_REF    490eb2ed3b6d0176bf6b2b3c6667c182559c8bb9
+#define QUICKCPPLIB_PREVIOUS_COMMIT_DATE   "2025-02-03 11:27:23 +00:00"
+#define QUICKCPPLIB_PREVIOUS_COMMIT_UNIQUE 490eb2ed