Examples

Platform spec article

Examples

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Spec standingStandard

Owner

Piotr Mikstacki pmikstacki@cybernomad.it

Submitter

Piotr Mikstacki pmikstacki@cybernomad.it

Current document

ADRs (2)

1. 0003-builtin-specs-sole-clif-source BUILTIN_SPECS is sole Cranelift import source Accepted

   Codegen must not invent alternate calling conventions for runtime builtins.

   Context

   Hand-written Cranelift calls bypass the shared ABI catalog and desynchronize JIT, AOT, and runtime extern "C-unwind" implementations.

   Decision

   Rule	Detail
   Catalog	BUILTIN_SPECS in beskid_abi::builtins is the sole source of Cranelift import signatures (ABI-002)
   Codegen	declare_builtin_imports builds FuncIds only from specs
   Diverging builtins	AbiReturnKind::Never for panic so unreachable blocks are correct
   Parity	Symbol strings in specs must match RUNTIME_EXPORT_SYMBOLS entries (ABI-001)

   Consequences

   New builtins require spec, BUILTIN_SPECS, symbols.rs, and beskid_runtime::builtins in one change set.

   Verification anchors

   compiler/crates/beskid_codegen; compiler/crates/beskid_abi/src/builtins.rs.

   Open full ADR page

2. 0004-runtime-c-unwind-exports Runtime builtins use C-unwind exports Accepted

   no_mangle extern C-unwind symbols implement the stable host surface.

   Context

   Generated code calls runtime entrypoints across JIT relink and AOT link. Rust panics across the boundary must use the platform unwind ABI expected by Cranelift call sites.

   Decision

   Rule	Detail
   Export attribute	Implementations use #[unsafe(no_mangle)] pub extern "C-unwind" in beskid_runtime::builtins
   Registry	RUNTIME_EXPORT_SYMBOLS lists every export the linker/JIT registers
   Layout types	BeskidStr { ptr, len } and BeskidArray { ptr, len, cap } are normative payload headers
   Families	Allocation, GC, fibers, channels, interop dispatch, IO, and panic share one catalog

   Consequences

   Host tooling resolves imports by symbol name + BUILTIN_SPECS signature, not Rust mangling.

   Verification anchors

   compiler/crates/beskid_runtime/src/builtins/mod.rs; compiler/crates/beskid_runtime/src/lib.rs re-exports.

   Open full ADR page

Articles

• Contracts and edge cases MUST rules for builtin signatures, return kinds, and export name stability. article Standard Reviewed Fri May 22
• Design model BuiltinFnSpec catalog, runtime export symbols, and codegen import boundaries. article Standard Reviewed Fri May 22
• Examples Reading BUILTIN_SPECS, mapping symbols to runtime modules, and typical call patterns. article Standard Reviewed Fri May 22
• FAQ and troubleshooting Builtin symbol drift, signature mismatches, and codegen/runtime debugging. article Standard Reviewed Fri May 22
• Flow and algorithm From lowering call sites through BUILTIN_SPECS to runtime C exports. article Standard Reviewed Fri May 22
• Verification and traceability Crate paths and tests that pin builtin specs to runtime exports. article Standard Reviewed Fri May 22

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Completeness

OKfeature · 2 SpecSection(s) · 1 H2 heading(s)

Section id	Required	Found
what-this-feature-specifies	yes	yes
implementation-anchors	yes	yes

Full tree: run pnpm verify:platform-spec-layout (writes src/generated/platform-spec-layout-report.json).

Related spec docs

• Feature
  Builtins and symbols

  Parent feature hub

Locating a builtin implementation

Given CLIF calling fiber_yield:

1. Find SYM_FIBER_YIELD → "fiber_yield" in symbols.rs.
2. Locate BuiltinFnSpec with symbol: SYM_FIBER_YIELD in builtins.rs.
3. Open compiler/crates/beskid_runtime/src/builtins/fiber.rs for behavior (park current fiber, requeue).

Corelib indirection

User code calls Fiber.Yield() in corelib_concurrency; lowering must not embed scheduler details. The package emits a call to fiber_yield only—see Concurrency package.

Allocation + GC root scenario

A global string cached from native code:

1. Lowering calls alloc with type descriptor pointer.
2. Host registers root via gc_register_root when exposing to foreign API.
3. On teardown, gc_unregister_root pairs with registration.

Missing unroot leaks until next collection; handles from gc_root_handle document temporary pinning.

Panic from bounds check

Lowering may emit:

call panic(message_ptr, message_len) -> never

Runtime formats output and terminates the process—no stack unwind through Beskid frames (error model legacy).

Inspecting JIT registration

In jit_module.rs, the declare_builtin_imports block maps each beskid_runtime function pointer to the symbol name Cranelift imports. A drift between Rust function export name and SYM_* constant breaks finalize with MissingFunction.

Related topics

• Verification and traceability
• Legacy symbol list: Runtime ABI (v0.1)