ten non-re-entrant, but sometimes useful.  |  |   
[ cpp-mmf ](https://github.com/carlomilanesi/cpp-mmf/) |  A C++98 library that encapsulates memory-mapped-files for POSIX or Windows  |  |   
[ cxxomfort ](https://ryan.gulix.cl/fossil.cgi/cxxomfort/) |  Backports of C++ features (C++11 to C++03 and C++1y proposals to C++11/C++03).  |  |   
[ Dlib ](https://dlib.net) |  Networking, threads, graphical interfaces, data structures, linear algebra, machine learning, XML and text parsing, numerical optimization, Bayesian nets, and numerous other tasks  |  Boost  |   
[ eventpp ](https://github.com/wqking/eventpp) |  A C++ event library for callbacks, event dispatcher, and event queue. With eventpp you can easily implement signal and slot mechanism, publisher and subscriber pattern, or observer pattern.  |  Apache 2.0  |   
[ fcppt ](https://fcppt.org/) |  Freundlich's C++ Toolkit (fcppt) is a collection of libraries focusing on improving general C++ code by providing better types and making use of functional programming.  |  |   
[ Folly ](https://github.com/facebook/folly) |  Facebook open-source library. A cross-platform library of C++14 components designed with practicality and efficiency in mind. ( [ Doc ](https://github.com/facebook/folly/blob/main/folly/docs) )  |  [ Apache-2.0 ](https://github.com/facebook/folly/blob/main/LICENSE) |  cmake, vcpkg   
[ GSL ](https://github.com/Microsoft/GSL) |  C++ Core **G** uidelines **S** upport **L** ibrary implementation, recommended by Bjarne Stroustrup, Herb Sutter and Co in [ C++ Core Guidelines ](https://isocpp.github.io/CppCoreGuidelines) |  [ MIT ](https://github.com/microsoft/GSL/blob/main/LICENSE) |  cmake, vcpkg   
[ gsl-lite ](https://github.com/martinmoene/gsl-lite) |  A version of ISO C++ Guideline Support Library (GSL) for C++98, C++11 and later  |  MIT  |  header-only   
[ GUL14 ](https://gul14.info/) |  General Utility Library for C++14 from [ DESY ](https://www.desy.de/) : Often-used utility functions and types, including String utilities, Statistics and Numeric functions, Containers, Debugging means, etc. ( [ Src ](https://github.com/gul-cpp/gul14) )  |  LGPL-2.1  |  meson, vcpkg   
[ History ](https://github.com/ryder052/History) |  Modern C++17 Undo/Redo Framework  |  [ Unlicense ](https://github.com/ryder052/History/blob/master/LICENSE) |   
[ hspp ](https://github.com/BowenFu/hspp) |  An experimental library to bring Haskell Style Programming to C++.  |  Apache-2.0  |  header-only   
[ IP-DOS (tm) ](https://github.com/ideafarm/ideafarm.home.1) |  IdeaFarm (tm) Piggyback Distributed Operating System: A general purpose programming environment for the C++ language.  |  Proprietary Open Source  |  Open Watcom 2.0   
[ JUCE ](https://www.juce.com/) |  An extensive, mature, cross-platform C++ toolkit  |  GPL  |   
[ Kangaru ](https://github.com/gracicot/kangaru) |  A dependency injection container for C++11 and C++14  |  MIT  |   
[ Kerbal ](https://github.com/WentsingNee/Kerbal) |  Backports of modern STL facilities to previous standard. More features! More constexpr!  |  LGPL-3.0  |  header-only; cmake   
[ libsourcey ](https://github.com/sourcey/libsourcey) |  A cross-platform C++14 library for high speed networking and media encoding. HTTP, WebSockets, TURN, STUN, Symple and more.  |  LGPL-2.1  |  cmake   
[ LLNL/units ](https://github.com/LLNL/units) |  A run-time C++ library for working with units of measurement and conversions between them and with string representations of units and measurements  |  BSD 3-Clause "New" or "Revised"  |  cmake   
[ Loki ](https://sourceforge.net/projects/loki-lib/) |  A C++ library of designs, containing flexible implementations of common design patterns and idioms.  |  MIT  |  make   
[ match(it) ](https://github.com/BowenFu/matchit.cpp) |  A lightweight pattern-matching library for C++17 with macro-free APIs.  |  Apache-2.0  |  header-only   
[ nonstd-lite ](https://github.com/martinmoene/nonstd-lite) |  A list of *-lite repositorie