This inheritance list is sorted roughly, but not completely, alphabetically:

[detail level 123]

Cdxx::utils::As< Range >
Cdxx::utils::Defer< TDeferred >	Class for deferring operations until the end of lifetime
Cdxx::errors::Errno	Tag type, helps indicate that errno info should be added to the error message
Cdxx::http::Errno
Cdxx::http::utils::File	RAII file descriptor
Cdxx::overload::fn_ptr_wrapper< Callable, Class, Ret, Args >	Class == int means free function (can't have a method on int)
CFOf< width >
CFOf< 32 >
CFOf< 64 >
Cdxx::http::HeaderCompare	HTTP headers comparison struct - they must be case-insensitive
CIOf< width >
CIOf< 16 >
CIOf< 32 >
CIOf< 64 >
CIOf< 8 >
Cstd::logic_error
Cdxx::assert::failure	A default error type that is thrown when the assertion fails
Cdxx::selftest::test_failure	The exception type used by test assertions
Cdxx::math::Norm< Func, SqFunc >	Defines a norm. Only norm field is required, all other fields can be assigned a nullptr
Cdxx::http::PathNode< TData >
Cdxx::http::PendingConnection< TResponse >	An awaitable object that allows the handler code to respond to the request at a later point in time
Cdxx::http::SimpleTask::promise_type
Cdxx::math::detail::RealOf< T >
Cdxx::math::detail::RealOf< T >
Cdxx::http::Request	HTTP request structure. Also used for multipart request data
Cdxx::http::Response	Server's response to the client
Cstd::runtime_error
Cdxx::errors::Error	Exception class that supports construction from std::format-like args and automatic errno capture in the message
Cdxx::http::ServerError	Exception class that supports construction from a format-like args and automatic errno capture in the message
Cdxx::http::RequestError
Cdxx::http::StreamError
Cdxx::http::Server	A simple HTTP server
Cdxx::http::SimpleTask	A single connection handler coroutine task
Cdxx::math::Sub	Default difference is subtraction
CTs...
Cdxx::overload::overload< Ts >	Overload pattern implementation. Itself does not differ from https://www.cppstories.com/2019/02/2lines3featuresoverload.html/, extra functionality comes from CTAD. See module description for usage
Cdxx::selftest::UnitTest< TFunc >	Create an object of that class to declare a unit test
CUOf< width >
CUOf< 16 >
CUOf< 32 >
CUOf< 64 >
CUOf< 8 >
Cdxx::overload::wrap_callable< T >
Cdxx::overload::wrap_callable< Ret(*)(Args...)>
Cdxx::overload::wrap_callable< Ret(Class::*)(Args...) && >
Cdxx::overload::wrap_callable< Ret(Class::*)(Args...) const >
Cdxx::overload::wrap_callable< Ret(Class::*)(Args...)>