P-3.5 Compiling, Linking and Build Tools

Work through these

• The four stages: preprocess, compile, assemble, link

  Each stage takes the previous stage's output and each can fail on its own terms. Running them separately once makes the whole process concrete rather than magical.

• Header files and the preprocessor, which only pastes text

  Including a header copies its text into your file before compiling begins, which is why a missing declaration and a missing definition are entirely different complaints.

• Undefined reference: a link error, not a compile error

  The compiler was satisfied that a function exists somewhere and the linker could not find it. Reading the message as a spelling problem rather than a missing library wastes a lot of time.

  NPTEL: Introduction to Programming in C · Course

• Static and dynamic libraries, and what ships with your program

  Library code can be copied into your executable or loaded when it starts, and the choice decides both the size of the file and whether it runs on a machine that lacks the library.

• A build tool rebuilds what changed, using file times

  A build file records which outputs depend on which inputs so that only the affected parts are rebuilt. Most confusing build behaviour comes from a dependency nobody declared.