Technical mental model

Struct and header design determines whether your project scales cleanly across files or collapses into dependency tangle. Good interface boundaries reduce both bugs and rebuild cost.

Struct layout includes alignment padding; physical size can exceed visible field sum.

Headers should expose contracts, not implementation internals.

Forward declarations reduce coupling where full type definition is unnecessary.

Equations and constraints that drive decisions

Practical struct size model:

Where:

• $padding$: alignment bytes inserted by compiler

Implementation walkthrough

Implementation sequence:

1. Keep public headers minimal and move heavy includes into source files.
2. Use include guards in every header and avoid cyclic include graphs.
3. Hide internal representation behind opaque handles when stability matters.
4. Audit binary layout assumptions when serialization or hardware mapping is involved.

Validation and debugging checklist

• Do not depend on implicit packing unless compiler settings are controlled and documented.
• Avoid exposing mutable internals unless callers are responsible for invariants.
• Break cycles with forward declarations, not duplicated declarations.
• Treat ABI-facing struct changes as compatibility events.

A clean header/struct strategy makes large C codebases maintainable and reviewable under change pressure.