GERC (gerc crate)

gerc is the Rust lowering and emission layer in the PARC -> LINC -> GERC toolchain.

It is the crate you use when you already have a normalized source contract and, optionally, evidence about native symbols or link plans. gerc then turns that input into Rust FFI output.

The target architecture is strict:

• gerc library code must not depend on parc or linc
• gerc owns its own generation model
• gerc consumes translated source and evidence inputs
• translation from PARC or LINC artifacts belongs only in tests, examples, or external harnesses
• there is no shared ABI crate and no backward-compatibility burden for discarded pipeline shapes

gerc generates Rust FFI bindings from C declarations. The output can be a standalone Rust source bundle or a Cargo-compatible crate directory, and it also emits plain rustc link arguments for non-Cargo toolchains.

One correction matters up front: the current public crate surface is broader than just generate() and generate_from_source(). The crate also exposes:

• a crate-owned C-side model under gerc::c
• explicit staged gate / lower modules
• consumer-side inspection and sidecar helpers

In the toolchain split:

• parc owns source meaning
• linc owns link and binary meaning
• gerc owns Rust lowering, Rust emission, and emitted build output

Audience

This book is for developers who:

• want to understand how gerc transforms C declarations into Rust FFI code
• need to integrate gerc as a library in their own tooling
• are building downstream consumers on top of gerc output

Scope

gerc is intentionally narrow:

Quick Start

#![allow(unused)]
fn main() {
use gerc::{generate_from_source, GercConfig, emit_source};
use gerc::intake::{SourceDeclaration, SourceFunction, SourcePackage, SourceType};

let mut source = SourcePackage::default();
source.declarations.push(SourceDeclaration::Function(SourceFunction {
    name: "init".into(),
    parameters: vec![],
    return_type: SourceType::Int,
    variadic: false,
    source_offset: None,
}));

let config = GercConfig::new("mylib_sys");
let output = generate_from_source(source, &config).unwrap();
let emitted = emit_source(&output.projection);
println!("{emitted}");
}

If validation evidence is present, gerc treats it as a gating input for functions and variables. Declarations without usable evidence are filtered out and reported through diagnostics instead of being emitted.