In the previous post , we watched the compiler transform optimized SSA into machine code bytes and package them into object files. Each .o file contains the compiled code for one package—complete with machine instructions, symbol definitions, and relocations marking addresses that need fixing. But your program isn’t just one package. Even a simple “hello world” imports fmt, which imports io, os, reflect, and dozens of other packages. Each package is compiled separately into its own object file. None of these files can run on their own.