1. Abstract
This RFC defines how Aura builds packages into artifacts: target graph (bin/lib/test), feature flags, profiles (dev/release), caching, cross-compilation, and the default product—a single native executable linking user code and the runtime.
The build orchestrator is implemented in Rust and invoked via aura build / aura check / aura test.
2. Motivation
2.1 Problem statement
Compilation alone is not enough: users need reproducible, incremental builds, profiles, and cross targets without writing bespoke scripts.
2.2 Why now
Packages (RFC-005) and compiler (RFC-004) need a graph executor; distribution (RFC-013) consumes outputs.
2.3 Success metrics
| Metric | Target |
|---|
| Default artifact | One executable path |
| Incremental | No-op rebuild ~instant when unchanged |
| Cross | Cross-compile to supported triples from CI |
3. Goals
- Clear target model and dependency graph.
dev vs release profiles with sensible defaults.- Cache compiled artifacts keyed by inputs.
- Cross-compile support for v1 platform matrix.
- Integration with tests and packaging.
4. Non-goals
- Generic multi-language monorepo build (Bazel replacement).
- Distributed remote execution in MVP.
- Dynamic plugin loading as default artifact type.
5. Prior art & alternatives
| System | Notes | Take |
|---|
| Cargo | Profiles, targets, features | Primary inspiration |
| Go build | Simple | UX contrast |
| Gradle | Flexible, heavy | Avoid |
| Make | Universal | Not primary UX |
6. Design
6.1 Overview
aura.toml targets
→ resolve packages ([RFC-005](/rfc/005))
→ build plan (topo units)
→ compile CGUs ([RFC-004](/rfc/004))
→ link runtime + objs
→ artifact in target/<profile>/
6.2 Targets
| Target kind | Output |
|---|
bin | Executable (default ship form) |
lib | Library for dependents (rlib-like intermediate) |
test | Test harness binary |
bench | Later |
example | Optional |
Default binary name from package name.
6.3 Profiles
| Profile | Goals |
|---|
dev | Fast compile, debuginfo, fewer opts, race detector optional |
release | LTO optional, strip, opts, no race detector |
test | Like dev + test cfg |
User custom profiles in aura.toml (later).
6.4 Features
- Additive feature flags on packages (Cargo-like).
default features set.- Unify across graph.
6.5 Caching
target/ directory layout versioned.- Key: compiler version, target triple, profile, features, source hash, dep hash.
aura clean removes artifacts.
6.6 Cross-compilation
--target <triple> for supported triples.- Toolchain ships or downloads sysroot/runtime libs for target (RFC-013).
- Linker selection documented per host.
6.7 Linking model
- Static link runtime by default → single file.
- Optional dynamic (non-default) for advanced.
- LTO: opt-in thin LTO for release when stable (not mandatory day-one).
6.8 Build scripts
- No arbitrary build scripts in MVP; declarative settings in
aura.toml only.
- If introduced later: sandboxed, no network default.
6.9 Examples
aura build
aura build --release -o dist/server
aura build --target aarch64-unknown-linux-gnu
aura check
6.10 Error model / edge cases
| Case | Behavior |
|---|
| Link error | Surface linker message + Aura context |
| Cache corrupt | Rebuild unit; integrity hash fail |
| Feature cycle | Resolve error |
6.11 Compatibility & migration
target/ format may bump with major toolchain.- Stable: CLI flags for profile/target/output.
7. Open questions
| # | Question | Options | Owner | Status |
|---|
| 1 | Thin LTO default on release? | opt-in first | Build | Resolved — opt-in |
| 2 | build scripts MVP? | no | Build | Resolved |
| 3 | Intermediate lib format | | Build | Resolved — no stable lib format MVP; source→obj→link; rlib-like later |
8. Rationale & trade-offs
Cargo-like graphs match the package model and developer expectations for compiled languages. Single-file default matches RFC-000. Avoiding build scripts early reduces supply-chain risk. Cost: less flexibility for exotic codegen until later.
9. Unresolved / future work
- Remote cache
- Workspaces build scheduling UX
- Compile pipeline metrics HTML report
10. Security & safety considerations
- No ambient network during build in MVP.
- Cache poisoning mitigated by content hashes.
- Untrusted build scripts (if ever) sandboxed.
11. Implementation plan (optional)
| Phase | Scope | Exit criteria |
|---|
| B0 | Single bin local target | aura build hello |
| B1 | Dep graph + cache | Rebuild incremental |
| B2 | Release + cross | Ship matrix CI |
12. References
Changelog
| Date | Author | Change |
|---|
| 2026-07-16 | | Lock no stable intermediate lib MVP; Status → Accepted |
| 2026-07-16 | | Status → In Review — Review: profiles/no-scripts direction solid; thin vs full build system |
| 2026-07-15 | | Initial skeleton |
| 2026-07-15 | | Solid draft: profiles, single binary link |
| 2026-07-15 | | Lock no build scripts MVP; LTO opt-in |
