address_info.h

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#ifndef A_UTIL_SYSTEM_ADDRESS_INFO_HEADER_INCLUDED
#define A_UTIL_SYSTEM_ADDRESS_INFO_HEADER_INCLUDED
 
#include <a_util/base/types.h> // handle_t
#include <a_util/filesystem/path.h>
 
namespace a_util {
namespace system {
 
class AddressInfo {
public:
#if ((defined _MSC_VER) && (_MSVC_LANG >= 201510L)) || (__cplusplus >= 201510L)
    // The noexcept-specification in C++17 is a part of the function type and
    // may appear as part of any function declarator.
    // See https://en.cppreference.com/w/cpp/language/noexcept_spec
    template <typename ReturnType, typename... Args>
    explicit AddressInfo(ReturnType (*const function)(Args...) noexcept) noexcept
        : _address{toDataPointer(function)}
    {
    }
#endif
 
    template <typename ReturnType, typename... Args>
    explicit AddressInfo(ReturnType (*const function)(Args...)) noexcept
        : _address{toDataPointer(function)}
    {
    }
 
    template <typename T>
    explicit AddressInfo(const T& variable) noexcept : _address(&variable)
    {
        static_assert(!std::is_function<T>::value,
                      "ERROR: CTOR for data pointer is called with function pointer");
    }
 
public:
    filesystem::Path getFilePath() const;
 
private:
    template <typename Return, typename... Args>
    const_handle_t toDataPointer(Return (*const function)(Args...)) noexcept
    {
        // According to the C-standard, casting a function pointer to a void* is not allowed.
        // It is however allowed to cast a function pointer to a function pointer of a different
        // type. Taking the address of the function pointer will return a data pointer.
        //
        // Read explanation from inner to outer static_cast.
        // Type punning, cast the data pointer back to a pointer to a data pointer and return the
        // address of the data pointer (const correctness)
        return *static_cast<void* const*>(
            // Type punning, cast the const data pointer (pointing to the function pointer) to
            // const void*
            static_cast<const void*>(
                // cast temporary function pointer to lvalue reference to const, which we can take
                // the address of. The address is the resulting data pointer pointing to the
                // function pointer
                &static_cast<Return (*const&)(Args...)>(function)));
    }
 
private:
    const_handle_t _address;
};
 
} // namespace system
} // namespace a_util
 
#endif // A_UTIL_SYSTEM_ADDRESS_INFO_HEADER_INCLUDED