About

This repository is to serve as a way to learn and experiment with how compilers, linkers, and the C runtime work cooperatively to make an application start, run, and shutdown. Most of the concepts and the mechanics involved are explained using examples from the examples directory.

Static Linking

Currently, we are limiting ourselves to static linking (both PIE and non-PIE variations). At some point in future, we might add information and examples about dynamic linking. In the meantime, interested readers can contribute dynamic linking related examples and topics.

Examples

Each example comes with its own README.md which explains what that example is trying to illustrate. General information about the examples, like suggested order of walking the examples, how to prepare a new example, how to build an existing example, is available in examples/README.md.

Prerequisites

This git repo has musl-libc, glibc, gcc and llvm-project as its submodules. This makes the repo self contained with respect to the compilers, libc and linkers one needs for experimentation. But, it also means that one will have to do a one-time build and setup of these compilers, libc and linkers. There is a convenience script, by name build_prereq.py, in the repo’s root directory which can build and set these up for use with experiments. Not suprisingly, build_prereq.py takes a long time to finish as GCC and Clang are built from sources. Note also that build_prereq.py does not install any dependencies required for building GCC and Clang. One will have to install such dependencies separately. Conveniently though, when build_prereq.py runs the configure step of say GCC, it will error out with an indicative message if GCC’s dependencies are missing.

Highlevel Concepts

Below are links to a few high level concepts that one can refer to when walking over the examples. They can also be read separate from the examples.