Overview

gerc sits between parc, linc, and downstream Rust tooling in the toolchain:

PARC  (source contracts)
  -> LINC  (link and evidence contracts)
  -> GERC  (Rust lowering and emission)
  -> generated Rust bindings crate or source bundle

Read this chapter as the workflow summary:

1. gerc receives its own input model
2. any upstream artifact translation happens outside gerc/src/**
3. gerc gates, lowers, and emits deterministic Rust and build artifacts

What Happens Inside GERC

1. Intake - gerc receives a GercInput wrapping source plus optional evidence. Tests/examples or external harnesses may translate PARC and LINC artifacts into that model.

2. Safety gating - Each declaration is checked against generation rules. Items that cannot be safely represented in Rust are rejected with diagnostics rather than guessed into existence.

3. Lowering - Accepted declarations are lowered from the crate-owned C-side model into RustProjection.

4. Type mapping - C types, pointers, arrays, function pointers, and qualifiers are mapped to Rust FFI-safe equivalents.

5. Emission - The projection is rendered into deterministic Rust source. Items are emitted in a stable order: constants, type aliases, enums, records, then extern "C" declarations.

6. Crate generation - Optionally, gerc writes a Cargo-compatible crate directory or a source bundle plus rustc link arguments.

Design Principles

• Deterministic - the same input always produces the same output
• Conservative - refuse generation rather than emit unsound code
• Library-first - gerc is a Rust library, not a CLI tool
• Generic - no fol-specific assumptions in the core crate
• Artifact-boundary integration - cross-package composition belongs outside gerc/src/**
• No back-compat burden - discarded shapes are deleted, not preserved