gistfile1.txt

    /** Constructor

        This constructs a non-owning pointer that
        points to the specified memory resource `r`.
        The caller is responsible for maintaining the
        lifetime of the pointed-to @ref memory_resource.

        @par Constraints
        @code
        std::is_convertible< T*, memory_resource* >::value == true
        @endcode

        @par Preconditions
        @code
        r != nullptr
        @endcode

        @par Exception Safety

        No-throw guarantee.

        @param r A pointer to the memory resource to use.
        This may not be null.
    */
    template<class T
#ifndef BOOST_JSON_DOCS
        , class = typename std::enable_if<
            std::is_convertible<T*,
                memory_resource*>::value>::type
#endif
    >
    storage_ptr(T* r) noexcept
        : i_(reinterpret_cast<std::uintptr_t>(
                static_cast<memory_resource *>(r)) +
            (json::is_deallocate_trivial<T>::value ? 2 : 0))
    {
        BOOST_ASSERT(r);
    }