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+ − 1 #ifndef TOML11_VERSION_HPP
+ − 2 #define TOML11_VERSION_HPP
+ − 3
+ − 4 // This file checks C++ version.
+ − 5
+ − 6 #ifndef __cplusplus
+ − 7 # error "__cplusplus is not defined"
+ − 8 #endif
+ − 9
+ − 10 // Since MSVC does not define `__cplusplus` correctly unless you pass
+ − 11 // `/Zc:__cplusplus` when compiling, the workaround macros are added.
+ − 12 // Those enables you to define version manually or to use MSVC specific
+ − 13 // version macro automatically.
+ − 14 //
+ − 15 // The value of `__cplusplus` macro is defined in the C++ standard spec, but
+ − 16 // MSVC ignores the value, maybe because of backward compatibility. Instead,
+ − 17 // MSVC defines _MSVC_LANG that has the same value as __cplusplus defined in
+ − 18 // the C++ standard. First we check the manual version definition, and then
+ − 19 // we check if _MSVC_LANG is defined. If neither, use normal `__cplusplus`.
+ − 20 //
+ − 21 // FYI: https://docs.microsoft.com/en-us/cpp/build/reference/zc-cplusplus?view=msvc-170
+ − 22 // https://docs.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=msvc-170
+ − 23 //
+ − 24 #if defined(TOML11_ENFORCE_CXX11)
+ − 25 # define TOML11_CPLUSPLUS_STANDARD_VERSION 201103L
+ − 26 #elif defined(TOML11_ENFORCE_CXX14)
+ − 27 # define TOML11_CPLUSPLUS_STANDARD_VERSION 201402L
+ − 28 #elif defined(TOML11_ENFORCE_CXX17)
+ − 29 # define TOML11_CPLUSPLUS_STANDARD_VERSION 201703L
+ − 30 #elif defined(TOML11_ENFORCE_CXX20)
+ − 31 # define TOML11_CPLUSPLUS_STANDARD_VERSION 202002L
+ − 32 #elif defined(_MSVC_LANG) && defined(_MSC_VER) && 1910 <= _MSC_VER
+ − 33 # define TOML11_CPLUSPLUS_STANDARD_VERSION _MSVC_LANG
+ − 34 #else
+ − 35 # define TOML11_CPLUSPLUS_STANDARD_VERSION __cplusplus
+ − 36 #endif
+ − 37
+ − 38 #if TOML11_CPLUSPLUS_STANDARD_VERSION < 201103L && _MSC_VER < 1900
+ − 39 # error "toml11 requires C++11 or later."
+ − 40 #endif
+ − 41
+ − 42 #endif// TOML11_VERSION_HPP