PARC

PARC is the C source frontend for the FOL toolchain. It preprocesses and parses one explicitly configured translation unit and produces the checked schema-v2 source contract consumed by later stages.

The package identity is follang-parc version 0.16.0; Rust code imports it as parc. The minimum supported Rust version (MSRV) is 1.89.

Public boundaries

• parc::scan::{ScanConfig, scan_headers} is the only public path that creates a source contract from headers.
• parc::contract contains immutable TargetSpec, SourcePackage, declaration and type values, canonical codecs, selection, and completion checks.
• parc::driver, parc::parse, parc::ast, and parc::visit remain available for syntax-level consumers.
• AST-to-contract lowering is internal. The old parc::ir, parc::intake, and direct public extraction routes do not exist.

Patching SourcePackage fields or deserializing its domain model directly is not supported. Build a checked package through scan_headers, or decode a canonical artifact with contract::decode_source_package.

Scanning

Scanning has no host/default constructor. Callers must supply:

1. a validated TargetSpec built from explicit compiler and C data-model facts;
2. a canonical PathMapping from absolute physical roots to logical roots;
3. PreprocessorMode::Builtin or an absolute external executable whose content fingerprint matches TargetSpec::compiler();
4. exactly one absolute entry header.

use parc::scan::{scan_headers, PathMapping, PathMappingRule, PreprocessorMode, ScanConfig};

let mapping = PathMapping::try_new([
    PathMappingRule::try_new("/absolute/project", "project")?,
])?;
let config = ScanConfig::new(checked_target, mapping, PreprocessorMode::Builtin)?
    .entry_header("/absolute/project/include/api.h");
let report = scan_headers(&config)?;

println!("declarations: {}", report.package().declarations().len());
println!("diagnostics: {}", report.diagnostics().len());

The bounded built-in path records original ranges, transitive content-addressed files, effective macros, include chains, and macro-expansion provenance. It may produce Completeness::Complete when every construct is modeled. Unsupported preprocessor behavior, parser recovery, exact-type gaps, and exhausted budgets produce structured forcing diagnostics instead of guessed data. External preprocessing remains explicitly Partial with PARC-P0001 because compiler output alone cannot prove original source and macro provenance.

Multiple entry headers must be scanned independently; they are never concatenated into one translation unit. Checked packages with identical target and preprocessing identity can be projected with SourcePackage::retain and combined with SourcePackage::merge.

Ownership

PARC owns source declarations, source types, diagnostics, provenance, target identity, and effective source inputs. It does not own measured ABI layout, symbol inspection, link planning, binary validation, or Rust generation.

Verification

Use the repository Make targets:

make fmt-check
make lint
make check-features
make test
make test-contract
make test-package
make test-system
make docs-check

make verify runs the full non-mutating release gate and requires all system prerequisites. See the book for the contract and parser details.

The three Cargo features are repository test switches, not consumer capability flags: repo-tests selects repository fixtures, system-tests selects declared compiler/header prerequisites, and dev-pegviz adds local reference-test tracing. The packaged archive promises its default library tests and doctests; repository-only fixtures are deliberately not included.

Distribution and compatibility

Registry publication is disabled (publish = false). The project does not claim that the follang-parc name is owned or available on crates.io. Release candidates are self-contained Cargo archives made from synchronized Git tags; downstream siblings pin the exact tag commit in PARC -> LINC -> GERC -> FOL order. make release-check is a non-mutating eligibility check and never bumps, tags, pushes, or publishes anything.

The current source artifact is schema follang.parc.source-package version 2, with ID algorithm version 1. Rust SemVer, schema/ID bump rules, MSRV policy, the exact H2 baseline, and the clean-upstream release procedure are recorded in RELEASE.md.

License

Dual-licensed under Apache 2.0 or MIT.