b9cfe2554f
Rewrote 20 issue writeups to the extern/runtime-class vocabulary (#foreign→extern, foreign_class_map→runtime_class_map, parseForeignClassDecl→parseRuntimeClassDecl, findForeignMethodInChain→findRuntimeMethodInChain, dedupeForeignSymbol→ dedupeExternSymbol, is_foreign_c_api→is_extern_c_api, stale filename refs to the renamed examples, foreign-class→runtime-class, bare foreign→extern). Renamed issues/0043-…-foreign-class-…→…-runtime-class-…. PHASE 9 COMPLETE — 9.4 GATE PASSES: zero 'foreign' across src/library/examples/ issues/docs/editors/specs/readme/CLAUDE, excluding only the SQLite API constant SQLITE_CONSTRAINT_FOREIGNKEY + vendored sqlite3.c/.h (upstream third-party). Suite green (644 corpus / 443 unit, 0 failed).
64 lines
2.4 KiB
Markdown
64 lines
2.4 KiB
Markdown
# 0030 — `extern G : T;` cross-file sx global declarations (feature request)
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> **Status: OPEN feature request** (not a bug). Relocated from the old
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> `examples/issue-0030.sx` placeholder during the test-layout migration. Repro:
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> `issues/0030-extern-global-declarations.sx` (currently a parse error — the
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> syntax doesn't exist yet).
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## Symptom / request
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Support an `extern G : T;` top-level form so a global **defined** in one sx
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source file can be **referenced** from another without threading it through
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parameters — mirroring how `extern` function declarations work (declared in one
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place, defined elsewhere, resolved at link time).
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```sx
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// game/main.sx
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g_metal_gpu : *MetalGPU = null;
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// game/chess/pieces.sx
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extern g_metal_gpu : *MetalGPU; // ← parse error today
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load :: (self: *ChessPieces, path: [:0]u8) {
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inline if OS == .ios {
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tex := g_metal_gpu.create_texture(w, h, .rgba8, xx pixels);
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}
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}
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```
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Today `pieces.load` takes `has_gpu: bool, gpu: GPU` params and `main.sx` threads
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them through; cross-file `extern` globals would drop that ceremony. Distinct from
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the existing `name : T extern;` form (an *external C* data symbol from
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libsystem etc. — see `examples/1205-ffi-extern-global.sx`); this request is for
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sx-defined globals shared across sx modules.
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## Reproduction
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`issues/0030-extern-global-declarations.sx`:
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```sx
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#import "modules/std.sx";
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extern g_x : *void; // want: a reference to a global defined elsewhere
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main :: () -> i32 { 0; }
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```
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`./zig-out/bin/sx run …` → `error: expected '::', ':=', or ':' after identifier`
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(the `extern` keyword/form is unparsed).
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## Implementation sketch
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- **parser** — surface syntax for `extern G : T;`. Must not clash with `G :: T;`
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(type alias), `G : T = ---;` (uninitialized global), `G : T;` (typed global).
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Reject `extern G : T = expr;` (an extern can't carry an initializer).
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- **src/ir/lower.zig** — record an extern-global stub that resolves at
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module-link time.
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- **src/ir/emit_llvm.zig** — emit an `external` LLVM global (no storage, just a
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reference). Globals already have first-class IR addresses; this adds an
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"extern" flag meaning "emit a reference, not storage."
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## Caveat
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Encourages process-global state. Steer callers toward explicit parameter passing
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where reasonable; reserve for genuine process singletons (active GPU, active
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platform) where threading through every call site is more noise than signal.
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