cib - Compile-time Initialization and Build

cib is a C++ header-only library for building embedded firmware with reusable components. It implements the compile-time initialization and build pattern. Instead of initializing components and registering callbacks at runtime, this process is executed at compile-time using constexpr or consteval functions.

Firmware using cib is implemented as a collection of components. Each component provides services and features to the build. Component features extend and provide new functionality to services.

As of the v1.0.0 release cib's API is considered stable and unlikely to change.

Sub-projects

There are multiple sub-projects contained within cib. Some of them are used to implement cib and others extend cib.

Services
- Flow - cib service used to compose sequences of dependent operations from multiple components.
- Callback - cib service used to implement simple callback/listener pattern.
Support
- string_constant - Compile-time string library with support for formatting similar to fmt/python format specifiers.
- log (wip) - Logging library.
- Container - Simple containers optimized for constexpr and/or free-standing applications.

Installing / Getting started

cib is released as a single header file as well as the zipped github repo. To get started quickly, download the cib.hpp header from the release area:

wget https://github.com/intel/compile-time-init-build/releases/download/v1.0.0/cib.hpp

Another option is to include cib as a git submodule in your repo and add the cib directory in your CMakeLists.txt file:

add_subdirectory(extern/compile-time-init-build)
target_link_libraries(your_target PRIVATE cib)

With either of these methods, include the cib.hpp header in your code to use it.

Hello, world!

Since cib is a library for efficiently building firmware through composition a simple example takes a few more lines than a typical "Hello, world!"

#include <cib/cib.hpp>
#include <iostream>

struct say_message : public cib::callback_meta<>{};

// the 'core' component exposes the 'say_message' service for others to extend
struct core {
    constexpr static auto config = cib::exports<say_message>;
};

// the 'say_hello_world' component extends 'say_message' with its own functionality
struct say_hello_world {
    constexpr static auto config =
        cib::extend<say_message>([](){
            std::cout << "Hello, world!" << std::endl;
        });
};

// the 'hello_world' project composes 'core' and 'say_hello_world'
struct hello_world {
    constexpr static auto config =
        cib::components<core, say_hello_world>;
};

// the nexus instantiates the project
cib::nexus<hello_world> nexus{};

int main() {
    // the fully extended and built services are ready to be used
    nexus.service<say_message>();
    return 0;
}

Try out this example live at Compiler Explorer.

A larger and more illustrative example can be found in this repo at examples/hello_world.

For more details on how to use cib, see the User Guide.

Building

cib is built with CMake. The single header is built with the release_header target:

git clone https://github.com/intel/compile-time-init-build.git
cmake -B build
cmake --build build -t release_header
ls build/include/cib/ | grep cib.hpp

This combines all the cib header files in the include tree by recursively including the #include directives and ignoring all other macros.

NOTE: cib uses CPM.cmake to fetch its dependencies. When first running cmake, the dependencies will be downloaded. To avoid re-downloading dependencies when reconfiguring cmake, it's recommended to designate a cache directory and set the CPM_SOURCE_CACHE environment variable.

Unit tests are registered with CTest, and will build and run as part of the built-in all target.

cmake -B build
cmake --build build

This will build and run all the unit tests with Catch2 and GTest. To re-run them:

ctest --test-dir build

Features

Compose modular firmware systems with high-level abstractions
Perform registration of components at compile-time
- 🏎 Optimize runtime-performance and memory usage
- 🦺 Catch undefined behavior during initialization

Contributing

If you'd like to contribute, please fork the repository and use a feature branch. Pull requests are warmly welcome.

For more details on contributing, please see CONTRIBUTING.md

Licensing

The code in this project is licensed under the BSL-1.0 license. See LICENSE for more details.

bryceschober/compile-time-init-build