18c43984e1
Route a bare 'extern' fn declare-only, exactly like a lib-less #foreign import. Six edits in decl.zig, each mirroring an existing foreign_expr guard so the empty-block placeholder body is never lowered: 1. funcWantsImplicitCtx: suppress the implicit __sx_ctx for .extern_ 2. declareFunction: add is_extern_decl 3. ...and include it in the C-ABI calling-convention promotion 4. lazyLowerFunction: .extern_ -> declareFunction (declare-only) 5. lowerFunction: .extern_ in the declare-only guard 6. lowerFunctionBodyInto: never promote/lower an extern stub examples/1223 now green: 'extern' abs lowers to 'declare i32 @abs(i32)' (external linkage, C ABI, no ctx param) and the call resolves against the default-linked libc -> abs(-7)=7, abs(42)=42. The 1.0b hand-authored snapshot matched byte-exact (no regen). Suite green (634 corpus / 443 unit). green commit (makes the 1.0b xfail pass; adds no new test).
77 lines
4.8 KiB
Markdown
77 lines
4.8 KiB
Markdown
# sx `extern`/`export` + `#foreign` retirement — Checkpoint (FFI-linkage stream)
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Companion to `current/PLAN-EXTERN-EXPORT.md` — one merged plan: **Part A** adds
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`extern`/`export`, **Part B** migrates `#foreign` and purges `foreign`. Update after
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every commit, one step at a time per the cadence rule.
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## Last completed step
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**Phase 1.1** (green) — wired extern fn lowering in `decl.zig`; example **1223 now
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green**, full suite green (634 corpus / 443 unit, 0 fail). A bare `extern` fn lowers
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exactly like a lib-less `#foreign` import: `declare i32 @abs(i32) #0` — external
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linkage, C ABI, NO `__sx_ctx` param; calls emit `call i32 @abs(i32 -7)` and resolve
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against the default-linked libc. Six edits, all routing `extern` declare-only
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(mirroring the `foreign_expr` guards): (1) `funcWantsImplicitCtx` suppresses ctx for
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`.extern_`; (2) `declareFunction` adds `is_extern_decl` and (3) includes it in the
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C-ABI promotion; (4) `lazyLowerFunction` routes `.extern_`→declare-only; (5)
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`lowerFunction` declare-only guard; (6) `lowerFunctionBodyInto` never promotes/lowers
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an extern stub. Hand-authored 1.0b snapshot matched byte-exact — no regen needed. No
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`.ir` snapshot added (the trivial `declare i32 @abs(i32)` doesn't warrant a 1000-line
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full-prelude dump; behavioral `.stdout` already catches ctx/linkage regressions).
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## Current state
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Syntax: bare `extern`/`export`, postfix after `callconv(.c)`, `extern ⇒ callconv(.c)`.
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**Decision 4 revised** (user 2026-06-14): `extern` carries an optional `LIB`+`"csym"`
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axis (`extern_lib`/`extern_name`) like `#foreign`; the `#library` decl + build-flag
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linking stays separate. **`extern` FUNCTIONS WORK** (import; bare form, no rename) —
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parse + lower complete, behavior-equivalent to a lib-less `#foreign` fn. Still TODO in
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Phase 1: the `extern LIB "csym"` lib/rename axis (fields exist, unconsumed) and the
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extern-global form. `export` not started (Phase 2). Part B `foreign` footprint to
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purge: 643 lines / ~57 identifiers in `src/` + 28 doc lines. End-state invariant:
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**zero `foreign`** (Phase 9.4 gate). **Done**: 0.0 tokens, 0.1 AST/parser plumbing,
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1.0a fn-path parsing + lib/name fields, 1.0b xfail example, 1.1 fn lowering (green).
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## Next step
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**Phase 1.2** (green) — two parts, each its own xfail→green or behavior-lock:
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1. **`extern LIB "csym"` rename for fns** — extend `parseOptionalExternExport()` (or
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`parseFnDecl`) to parse the optional `LIB` ident + `"csym"` string after the
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keyword into `FnDecl.extern_lib`/`extern_name`; consume them in `declareFunction`
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(mirror the `#foreign` c_name block at `decl.zig:~2119`: declare under the C name,
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map sx→C in `foreign_name_map`/dedupe). New example renaming a libc symbol (e.g.
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`c_abs :: (n: i32) -> i32 extern "abs";`).
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2. **extern-global `g : T extern [LIB] ["csym"];`** — parse path at `parser.zig:425`
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(the var-decl with type annotation): accept postfix `extern` → set
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`VarDecl.is_extern`/`extern_lib`/`extern_name`; lower like the `#foreign` global
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(`decl.zig:~1115-1137`, `.is_extern = vd.is_foreign`). New example mirroring
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`examples/1205-ffi-foreign-global` with `extern`.
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Stop at end of Phase 1 (do NOT start Phase 2 `export` or Part B migration). Then the
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A→B gate: a unit test that `#foreign` and `extern` lower to identical IR.
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## Open decisions
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Part A ratified (bare / postfix / `⇒ callconv(.c)` / lib-separate). Part B (confirm
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before Phase 9): runtime-class rename target — `Runtime*Class*` (recommended);
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historical carve-out — keep `issues/*.md` provenance, gate the live tree only.
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## Log
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- (init) Plan written; FFI-linkage stream opened.
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- (merge) Folded FOREIGN-MIGRATION in as Part B; deleted the split plan + checkpoint.
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- (0.0) Added `kw_extern`/`kw_export` tokens + keyword-map entries + LSP keyword
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classification + `lex linkage keywords` test. Suite green; no identifier collisions
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in the corpus. `lock` commit.
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- (0.1) Added `ast.ExternExportModifier` + `FnDecl.extern_export` +
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`VarDecl.is_extern`/`extern_name` + `parseOptionalExternExport()` (unconsumed) + 2
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parser unit tests. Suite green (443/633). `lock` commit.
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- (1.0a) Wired fn-path extern parsing (`parseFnDecl` + both lookahead predicates) +
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added `FnDecl.extern_lib`/`extern_name` + `VarDecl.extern_lib` per user feedback
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(decision 4 revised: extern carries an optional lib axis). Unconsumed by lowering.
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Suite green (443/633). `lock` commit.
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- (1.0b) Added `examples/1223-ffi-extern-fn.sx` + hand-authored success snapshots.
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RED (634 ran, 1 failed — sema `body produces no value`). `xfail` commit; 1.1 greens it.
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- (1.1) Wired extern fn lowering (6 edits in `decl.zig`, all declare-only routing
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mirroring `foreign_expr`): `funcWantsImplicitCtx` + `declareFunction` cc +
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`lazyLowerFunction`/`lowerFunction`/`lowerFunctionBodyInto` guards. 1223 green;
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`declare i32 @abs(i32)` (C ABI, no ctx). Suite green (634/443). `green` commit.
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## Known issues
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None yet.
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