Toolchain & Linking

gcc main.c hides four programs and a small mountain of conventions. This branch opens them up: preprocess → compile → assemble → link, what an object file contains, how the linker resolves symbols, the ELF format, static vs dynamic linking, and the loader that maps it all into a running process. Then the discipline half: gdb/lldb, sanitizers (ASan/UBSan/TSan), and valgrind — the tools that turn "it crashed" into a precise diagnosis.

Linking is where separate compilation, libraries, and the loader meet. Understand it and "undefined reference" / "symbol not found" stop being mysteries.

Planned notes

• The pipeline: preprocess → compile → assemble → link
• Object files and what's inside them
• The ELF format (sections, segments, headers)
• Symbols: definition, reference, and resolution
• Static linking and archives (.a)
• Dynamic linking and shared libraries (.so)
• The dynamic loader, relocation, PLT and GOT
• gcc vs clang and the compiler driver model
• make and the build dependency graph
• cmake (when make isn't enough)
• gdb / lldb essentials for low-level debugging
• Sanitizers: ASan, UBSan, and TSan
• valgrind and profilers (perf, cachegrind)

Core sources

• John Levine — Linkers and Loaders — the spine of this branch.
• Ian Lance Taylor — Linkers (20-part series) — how a linker really works, from the gold author. lwn.net/Articles/276782
• Ulrich Drepper — How To Write Shared Libraries — dynamic linking in depth. akkadia.org/drepper/dsohowto.pdf
• David Drysdale — Beginner's Guide to Linkers — the gentle on-ramp. lurklurk.org/linkers/linkers.html
• ELF specification; Clang sanitizer docs (clang.llvm.org/docs); GDB manual (sourceware.org/gdb).

Connects to: Assembly & Compiler Output · C from the Metal · OS from Scratch