Tools to alert users of messages (including errors and warnings) in a consistant manner.

There are a handful of notification types to consider:

  • Message: A simple notification.

  • Verbose: Optional messages that can be activated by category.

  • Warning: Something looks suspicious, but is not technically a problem (don’t exit)

  • Error: Something has gone horribly wrong and is impossible to recover from (exit)

  • Exception: Something didn’t go the way we expected, but we can still recover (exit if not handled)

  • Debug: A simple notification that should only be printed when NDEBUG is not set (don’t exit)

Messages default to “standard out”; all of the other default to “standard error”. Handling of these notifications can all be overriden by either whole category or by specific tag.

There are three possible recipients for all errors/warnings.

  • The end-user if the problem stems from inputs they provided to the executable.

  • The library user if the problem is due to mis-use of library functionality.

  • The library developers if something that should be impossible occurs.

The content of this file primarily targets the first group; developers should prefer asserts to ensure that supposedly “impossible” situations do not occur.


  • Whenever possible, exceptions should be preferred. They are more specific than warnings and can be responded to rather than automatically halting execution like errors.

  • Warnings should always detail what should be done differently to surpress that warning.


Status: ALPHA

namespace notify


using id_t = std::string
using message_t = std::string
using except_data_t = std::any
using id_arg_t = const id_t&
using message_arg_t = const message_t&
using response_t = bool(id_arg_t, message_arg_t, except_data_t)
using exit_fun_t = std::function<void(int)>


enum class Type


enumerator MESSAGE
enumerator DEBUG
enumerator WARNING
enumerator ERROR
enumerator EXCEPTION
enumerator NUM_TYPES


static id_t TypeID(Type type)

Convert a type to a human-readable string.

static id_t ColorTypeID(Type type)

Convert a type to a human-readable string in COLOR.

static NotifyData &GetData()

Central call to obtain NotifyData singleton.

inline auto &MessageHandlers()
inline auto &DebugHandlers()
inline auto &WarningHandlers()
inline auto &ErrorHandlers()
static void AddExitHandler(exit_fun_t fun)
static void ClearExitHandlers()
static void ReplaceExitHandlers()
template<typename ...FUN_Ts>
static void ReplaceExitHandlers(exit_fun_t fun, FUN_Ts... extras)
static void Exit(int exit_code)

Generic exit handler that calls all of the provided functions.

template<typename ...Ts>
static bool Notify(Type type, Ts... args)

Generic Notification where type must be specified.

static void Pause()
static void Unpause()
template<typename ...Ts>
static bool Message(Ts... args)

Send out a regular notification.

template<typename ...Ts>
static bool Debug(Ts... args)

Send out a DEBUG notification.

template<typename ...Ts>
static bool Warning(Ts... args)

Send out a notification of a WARNING.

template<typename ...Ts>
static bool Error(Ts... args)

Send out a notification of an ERROR.

template<typename ...Ts>
static bool TestWarning(bool test, Ts... args)
template<typename ...Ts>
static bool TestError(bool test, Ts... args)
template<typename FUN_T>
static HandlerSet &AddHandler(id_arg_t id, FUN_T fun)

Add a handler for a particular exception type.

template<typename FUN_T>
static HandlerSet &AddHandler(FUN_T fun)

Add a generic exception handler.

static HandlerSet &Ignore(id_arg_t id)

Ignore exceptions of a specific type.

static void SetVerbose(std::string id, bool make_active = true)

Turn on a particular verbosity category.

template<typename ...Ts>
static bool Verbose(const std::string &id, Ts... args)

Send out a notification of an “verbose” message.

static bool Exception(id_arg_t id, message_arg_t message = "", except_data_t except_data = 0)

Send out a notification of an Exception.

static const vector<ExceptInfo> &GetExceptions()

Retrieve a vector of ALL unresolved exceptions.

static ExceptInfo GetException(id_arg_t id)

Retrieve the first unresolved exception with a given id.

static size_t CountExceptions()

Return a total count of how many unresolved exceptions are left.

static size_t CountExceptions(id_arg_t id)

Return a total count of how many unresolved exceptions have a given id.

static bool HasExceptions()

Identify whether there are ANY unresolved exceptions.

static bool HasException(id_arg_t id)

Identify whether there are any unresolved exceptions with a given id.

static void ClearExceptions()

Remove all unresolved exceptions.

static void ClearException(id_arg_t id)

Remove first exception with a given id.


static constexpr size_t num_types = static_cast<size_t>(Type::NUM_TYPES)
struct ExceptInfo
#include <notify.hpp>

Information about an exception that has occurred.

Public Members

id_t id = "__NONE__"

Which exception was triggered?

message_t message = ""

A detailed message of this exception.

except_data_t data

Extra data needed to resolve this exception.

class HandlerSet
#include <notify.hpp>

Public Functions

inline HandlerSet()
HandlerSet(const HandlerSet&) = default
HandlerSet(HandlerSet&&) = default
inline ~HandlerSet()
inline bool GetExitOnFail() const
inline HandlerSet &SetExitOnFail(bool _exit = true)
inline bool Trigger(id_arg_t id, message_arg_t message, except_data_t except_data)

Trigger all handlers associated with a given ID.

inline bool Trigger(id_arg_t id, message_arg_t message)
inline bool Trigger(const ExceptInfo &info)
inline HandlerSet &Add(fun_t in)
inline HandlerSet &Add(fun_no_data_t in)
inline HandlerSet &Add(fun_msg_only_t in)
inline HandlerSet &Clear()
inline void Replace()

Replace all handlers with nothing (i.e., clear them)

template<typename ...FUN_Ts>
inline void Replace(fun_t in, FUN_Ts... extra)

Replace all handlers with the generic ones provided.

Private Types

using fun_t = std::function<response_t>
using fun_no_data_t = std::function<bool(id_arg_t, message_arg_t)>
using fun_msg_only_t = std::function<bool(message_arg_t)>

Private Members

vector<fun_t> handlers
bool exit_on_fail = false
struct NotifyData
#include <notify.hpp>

Staticly stored data about current notifications.

Public Functions

inline HandlerSet &GetHandler(Type type)
inline NotifyData()

Public Members

std::unordered_map<id_t, HandlerSet> handler_map
std::unordered_map<std::string, bool> verbose_map
vector<exit_fun_t> exit_funs
vector<ExceptInfo> except_queue
vector<ExceptInfo> pause_queue
bool lethal_exceptions = true
bool is_paused = false