Export attribute

Platform spec article

Export attribute

Back to Export and callbacks ◎ Open feature in platform map

Spec standingStandard

Owner

Piotr Mikstacki pmikstacki@cybernomad.it

Submitter

Piotr Mikstacki pmikstacki@cybernomad.it

Current document

ADRs (4)

1. 0001-hub-authority Feature hub owns normative contract Accepted

   Beskid-to-foreign export authority.

   Context

   Export/callback rules were scattered between runtime and language-meta drafts.

   Decision

   This feature hub must own normative MUST/SHOULD for Beskid export and callback registration (user interop).

   Consequences

   Distinct from runtime builtin exports on Rust ABI profile.

   Verification anchors

   /platform-spec/language-meta/interop/export-and-callbacks/

   Open full ADR page

2. 0002-distinct-from-runtime-builtins User export distinct from runtime builtins Accepted

   Export symbols are generated; builtins stay beskid_abi.

   Context

   Plugin authors confused generated exports with frozen JIT builtin tables.

   Decision

   User export symbols are generated from Beskid compilation units. Frozen runtime builtin exports remain on beskid_abi / Rust ABI profile — export-only work must not change BESKID_RUNTIME_ABI_VERSION.

   Consequences

   Codegen plans export metadata beside ExternImport; trampolines use runtime TLS hooks.

   Verification anchors

   /platform-spec/language-meta/interop/export-and-callbacks/ implementation anchors.

   Open full ADR page

3. 0003-export-pub-functions-v03 Export on pub functions v0.3 Accepted

   Contract vtables as Standard export remain out of scope.

   Context

   Embedding hosts need a minimal stable export surface before full vtable stories.

   Decision

   v0.3 Standard must support [Export] on pub functions with FFI-permitted types. Exporting arbitrary contract vtables as Standard is out of scope for v0.3.

   Consequences

   Callback registration table protocol is Standard; foreign-thread entry without host contract is Proposed v0.3.2+.

   Verification anchors

   export attribute; callback registration.

   Open full ADR page

4. 0004-spec-standard-impl-may-trail Standard spec implementation may trail Accepted

   Normative text can lead reference compiler export support.

   Context

   v0.3 is spec-first for interop; codegen for export is still landing.

   Decision

   This feature is Standard in v0.3 specification. Reference compiler support may trail; verification article records gaps until codegen lands.

   Consequences

   Contributors implement against ADRs without downgrading spec status to Proposed.

   Verification anchors

   verification and traceability.

   Open full ADR page

Articles

• Callback registration Host registration table protocol for Beskid exports invoked from foreign code (v0.3). article Standard Reviewed Sat May 23
• Export attribute Normative Export metadata for pub functions exposed to foreign hosts (v0.3). article Standard Reviewed Wed May 20
• Export and callbacks — Verification and traceability Conformance fixtures for Export and callback registration (v0.3). article Standard Reviewed Sat May 23

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Completeness

OKfeature · 3 SpecSection(s) · 1 H2 heading(s)

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

Related spec docs

• Feature
  Export and callbacks

  Parent feature hub

Placement

Export applies to pub function definitions only in v0.3 Standard. Contract methods, types, and modules must not use Export until a future profile promotes contract vtables.

Attribute fields

Field	Required	Meaning
Abi	yes	"C" for v0.3 Standard
Symbol	no	Exported linker symbol; default is the Beskid function name (unmangled)

Example:

[Export(Abi:"C", Symbol:"beskid_plugin_init")]
pub i64 plugin_init(i64 host_api_version) {
    return 0;
}

Permitted signatures

Export functions must use the same type set as Extern import methods in v0.3.0 (interop view types).

Linkage

Exported symbols must be emitted with global linkage visible to the platform linker. The build driver must include Beskid-generated objects and the runtime static archive per backend docs.

Panics

Panics in exported functions must be treated as non-returning traps across the boundary (error and unwind).