C Preprocessor Primitives for Structured Programming

• Motivation
• Tutorial
• Installation
  • Local Test And Install
  • Local Install Only
• Documentation

Motivation

Using the C preprocessor to generate code, while often derided, is sometimes useful. From generating self-serializing enums to instantiating template classs over a range of types, even modern, well structured C++ code can sometimes benefift from simple code generation using the preprocessor. Since the preprocessor was not designed with explicit iteration or other common high-level programming concepts, creating well-structured preprocessor code can be challenging.

The pp library is a light-weight, header-only, macro library providing primitives such as lists, sequences, conditionals and map operations, designed to facilitate using the C processor in a well-structured, functional manner.

The following snippet demonstrates generating class template instatiations for several types.

#include "core/pp/pp.h"

#define GEN_MYCLASS(N,T) template<> class N<T>;
#define GEN_MYCLASS_SEQ(SEQ) CORE_PP_EVAL_MAP_WITH_SEQ(MYCLASS,MyClass,SEQ)
#define TYPE_SEQ (int8, int16, int32, int64)

GEN_MYCLASS_SEQ(TYPE_SEQ)

Running through the preporcessor, generates the following code.

template<> class MyClass<int>; template<> class MyClass<long int>; template<> class MyClass<unsigned int>;

Yes, if only we could get the preprocessor to emit some newlines.

Tutorial

Installation

Local Test and Install

git clone https://github.com/cpp-core/pp
mkdir pp/build && cd pp/build
CC=clang-mp-16 CXX=clang++-mp-16 cmake .. -DCMAKE_INSTALL_PREFIX=~/opt
make -j4 check
make install

Local Install Only

git clone https://github.com/cpp-core/pp
mkdir pp/build && cd pp/build
CC=clang-mp-16 CXX=clang++-mp-16 cmake .. -DCMAKE_INSTALL_PREFIX=~/opt -DPP_TEST=OFF
make install

Use FetchContent To Add At Cmake Buildtime

Add the following snippet to your cmake file and add pp::pp to your targets.

include(FetchContent)
FetchContent_Declare(cpp_core_pp GIT_REPOSITORY https://cpp-core/pp GIT_TAG main FIND_PACKAGE_ARGS)
FetchContent_MakeAvailable(cpp_core_pp)

Use Cpp-Core Manager To Add Any Compatible Repo

Add the following snippet to your cmake file. You can then include any compatible library with the add_repo call.

if(NOT CPP_CORE_CMAKE_DIR)
  include(FetchContent)
  set(NAME cpp_core_cmake)
  FetchContent_Declare(
    ${NAME}
    GIT_REPOSITORY https://github.com/cpp-core/cmake
    GIT_TAG main
    )
  FetchContent_MakeAvailable(${NAME})
  set(CPP_CORE_CMAKE_DIR ${CMAKE_BINARY_DIR}/_deps/${NAME}-src)
endif()

include(${CPP_CORE_CMAKE_DIR}/utils/all.cmake)
include(${CPP_CORE_CMAKE_DIR}/recipes/all.cmake)

add_repo(cpp-core/pp)