Awesome

awesome-c-preprocessor

A list of awesome C preprocessor stuff

Hirrolot/metalang99 -- Full-blown preprocessor metaprogramming.
boostorg/preprocessor -- Boost.org preprocessor module.
boostorg/vmd -- Boost.org VMD module.
rofl0r/order-pp -- order-pp preprocessor library (standalone part of chaos-pp).
rofl0r/chaos-pp -- chaos preprocessor library. this is what boost preprocessor derived from.
pfultz2/Cloak -- A mini-preprocessor library to demonstrate the recursive capabilities of the preprocessor.
pfultz2/ZLang -- A plugin framework for namespace macros in C/C++.
mcinglis/libpp -- Functional-programming macros for the C preprocessor.
mcinglis/macrofun -- Standards-defying functional-programming macros for the C preprocessor.
gustedt/p99 -- Macros and functions for C99.
davidgarland/ceano -- A collection of C preprocessor hackery.
twhitehead/c99-meta -- Abusing the C99 preprocessor for meta-programming.
metacall/core/source/preprocessor -- Preprocessor Library by Parra Studios.

Hirrolot/datatype99 -- Algebraic data types for C99.
Hirrolot/interface99 -- Zero-boilerplate interfaces for C99.
orangeduck/Cello -- Higher level programming in C.
CObjectSystem/COS -- C Object System: a framework that brings C to the level of other high level programming languages and beyond.
small-c/obj.h -- A single-header supports OOP in pure C.
shakna-israel/LetsDestroyC.md -- Let's Destroy C.
yulon/clofn -- A closure function implementation for C.
alexanderchuranov/Metaresc -- META data and RESource library for C language.
Leushenko/C99-Lambda -- Purely evil preprocessor macros adding anonymous functions and closures to ISO C99.
Leushenko/Pyrite -- BASIC-style "compiler" as C syntax library.
emdash/goof -- A toy functional language created through the abuse of C.
Qqwy/c_exceptional -- A simple Exception-handling library for C99.

BlueFlo0d/CSP -- Compile-time LISP interpreter on C macro preprocessor.
cospplredman/PPLISP -- A set of 45 macros that allow for lisp-like preprocessor meta programming.
Ferdi265/preprocessor_brainfuck -- A brainfuck interpreter using only the C preprocessor.
orangeduck/CPP_COMPLETE -- Brainfuck interpreter written in the C preprocessor.
mkotha/bfi -- A brainfuck interpreter on the C preprocessor.
notfoundry/bf.h -- Brainfuck interpreter written in the C preprocessor.
notfoundry/ppasm -- x86_64 macro assembler entirely in C preprocessor.

ptaffet/preprocessor-debug -- Observe how the C preprocessor expands your complicated macros.
notfoundry/ppstep -- Interactive C/C++ preprocessor macro debugger.
messer-cpp/messer -- REPL for C preprocessor of C++17.

mcpp -- A portable C preprocessor.
swansontec/map-macro -- A recursive C preprocessor macro which performs an operation on each element of a list.
M4GNV5/CppFun -- Math in the C pre-processor by breaking up Numbers into arrays of 8 bits and implementing common operations on those arrays.
ramdeoshubham/macros -- A collection of commonly used C MACROS.
agrif/Makefile -- A horrible, horrible, wonderful C Preprocessor hack library.
notfoundry/wtf.c -- 4-bit ALU metaprogrammed in C11's _Generic.
kcning/binom -- C macro that computes binominal coefficient at compile time.
ldionne/cisp -- A C preprocessor library implementing object semantics.
rofl0r/thread_wrapper -- A thread launcher wrapper macro which removes the boilerplate and allows to call any non-void function as a separate thread (needs BOOST preprocessor lib, which is C compatible).
18sg/uSHET -- A Malloc-Free SHET Client Library for Microcontrollers (lib/cpp_magic.h).
ScrimpyCat/CommonC -- Common utilities for C (CommonC/Template.h).
cher-nov/Gena -- Generic pseudo-templated containers for C. Written entirely in C89 with design inspired by the C++ STL.
DiscordPP/discordpp and DiscordPP/plugin-native -- A modular Discord library and a module for it that use macros to define Discord API endpoints and objects.

Some worth-noting articles: