Linkers and loaders

About the book

John R. Levine's book examines linkers and loaders, the tools that bind abstract names in source code to concrete addresses and symbols a machine can use. The subject sits at a seam most programmers cross daily without looking: object files, symbol tables, relocation, shared libraries, and the handoff from executable file to process. Levine treats these as engineering problems with concrete formats and algorithms.

The book covers static linking, dynamic linking, relocation and address assignment, and the loader's role at program startup. It discusses object file formats and the practical machinery behind them, including the conventions that let code compiled in different languages or at different times work together. The treatment is grounded in real systems rather than a single idealized model.

Levine writes as a practitioner explaining mechanisms to other practitioners. The prose favors definitions, diagrams of data structures, and worked descriptions of how tools resolve symbols and patch addresses. Readers come away with a mental model of the build-and-launch pipeline that survives changes in specific toolchains.

How to read it

Read with an executable and a toolchain nearby. The material rewards pausing to inspect an object file, list symbols, or trace which library supplies a function. Treat the format descriptions as maps to compare against what your own compiler and linker actually emit.

The book is technical and assumes comfort with C, assembly-level concepts, and operating system basics. Some format details reflect the systems of its era, so expect to supplement them with current documentation. The concepts age better than the specifics.

Who it suits

Programmers who have hit confusing linker errors, maintain build systems, write plugins or shared libraries, or work on embedded and systems software will find the explanations useful. Compiler and operating system students benefit from seeing the stage between code generation and execution. Anyone content to treat the build as a black box can skip it.

Reading considerations

The book predates many current toolchain conventions, so format and platform details may not match today's defaults. Check which systems it addresses before relying on it for a specific platform. The core ideas about symbols, relocation, and loading remain worth testing against your own tools.