d8076b9333
Surface rename of the signed integer family: s1..s64 become i1..i64
(u1..u64, usize, isize unchanged). 'string' keeps the s-prefix arm in
name classification; width parsing moves to the i-prefix arm next to
isize.
Internal TypeId tags follow the surface (.s8/.s16/.s32/.s64 ->
.i8/.i16/.i32/.i64), as do mono-key mangle fragments (ptr_i64,
tu_i64_bool) and all display/diagnostic formatting (i{d}).
Migrated in the same sweep: stdlib + examples + issue repros + FFI C
companions (shared symbol names like ffi_id_i64), expected
stdout/stderr/ir snapshots, specs.md, readme.md, CLAUDE.md/AGENTS.md,
implementation_plan.md, docs/, issue writeups. Vendored stb_image and
historical flow state left untouched.
zig build test: 426/426; examples suite: 595/595.
109 lines
4.9 KiB
Markdown
109 lines
4.9 KiB
Markdown
# 0057 — `xx`-to-Any variadic arg inside an imported-module function segfaults
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## ✅ RESOLVED
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Root cause: when lowering a variadic-pack call (`lowerPackCall` in
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`src/ir/lower.zig`), the pack args were lowered with whatever `self.target_type`
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happened to be set to from the surrounding context. For a bare arg this is
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harmless (`inferExprType` ignores `target_type`), but `xx <expr>`'s result type
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IS `target_type` — so `format("…", xx i)` inside a `-> string` function cast the
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int to `string`, monomorphized `__pack_string`, and ABI-coerced the 4-byte int
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as a 16-byte string fat pointer → memory corruption. (Inline it happened to work
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because `target_type` was null there; the imported-module path left it set.)
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Fix: clear `self.target_type` (save/restore) around the pack-arg lowering loop —
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a pack arg is independently typed (comptime `..$args` auto-boxes to `Any`; a
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value pack takes its element/protocol type), never coerced to a leftover outer
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target. Regression: `examples/242-xx-any-pack-cross-module.sx` (+ companion
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`242-xx-any-pack-cross-module/fmt.sx`). Gates: zig build, zig build test, 279
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examples pass. The original symptom/repro/investigation notes are kept below.
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## Symptom
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A `format(...)` / `print(...)` call whose variadic arg is an **explicit `xx`
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cast to `Any`** segfaults at runtime (`__platform_memmove`, an Any-box/string
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copy corruption) **when the call is inside a function defined in an imported
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module**. The identical code works (a) inline in the main file, and (b) in an
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imported module if the arg is passed *without* `xx` (auto-boxed).
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- **Observed:** `Segmentation fault at address 0x1...` in `__platform_memmove`,
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via `runJITFromObject` (target.zig:244). Crashes for any int width (i32, u64).
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- **Expected:** prints the formatted string, same as the auto-boxed / inline
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forms.
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## Reproduction
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`library/modules/zz_repro.sx`:
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```sx
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#import "std.sx";
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build :: (n: i32) -> string {
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result := "x:\n";
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i : i32 = 0;
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while i < n {
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line := format(" item {}\n", xx i); // <-- xx cast to Any is the trigger
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result = concat(result, line);
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i = i + 1;
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}
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result;
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}
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```
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Driver (e.g. `.sx-tmp/repro.sx`):
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```sx
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#import "modules/std.sx";
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m :: #import "modules/zz_repro.sx";
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main :: () -> i32 { print("[{}]", m.build(2)); return 0; }
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```
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Run: `./zig-out/bin/sx run .sx-tmp/repro.sx` → segfault.
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### Isolation (what is / isn't the trigger)
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- **Auto-box works:** change `xx i` → `i` in the module → prints fine.
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- **Inline works:** put the same `build` body (with `xx i`) directly in the
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driver's `main` (no import) → prints fine.
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- **Width-independent:** `xx` on an `i32` or a `u64` both crash.
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- So the trigger is specifically: **explicit `xx <int>` → Any as a variadic
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`format`/`print` arg, in a function that lives in an imported module.**
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The crash blocked ERR step E3.3 (`library/modules/trace.sx`), whose
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`trace.to_string()` formatted each frame with `format("... {}\n", i, xx frame)`
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where `frame : u64` — exactly this pattern. (Dropping the `xx` would dodge it,
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but per the project STOP rule that workaround is not taken; the trace formatter
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waits on this fix.)
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## Investigation prompt
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The bug is in how an explicit `xx`-to-`Any` cast lowers for a variadic argument
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when the enclosing function is monomorphized/emitted as part of an **imported
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module** (vs the root module). Auto-boxing (the implicit `T → Any` coercion at
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the variadic call site) produces correct code; the explicit `xx` path does not,
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but only across the module boundary — strongly suggesting the `xx`→`Any`
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box (`box_any` / `boxAny` in `src/ir/lower.zig` + `src/ir/emit_llvm.zig`'s
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`.box_any` arm) emits a value/width that the variadic-pack marshalling
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(`any_to_string` / the `#insert build_format` arg materialization in
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`library/modules/std.sx`) then `memmove`s incorrectly — possibly a stale
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`source_type`, a pointer-vs-value confusion, or the imported-module emit losing
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the box's type so the fat-pointer/string copy reads garbage.
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Suspected area:
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- `src/ir/lower.zig`: the `unary_op .xx` → `coerceToType(..., .any)` /
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`boxAny` path, and how variadic args are collected for `format`/`print`
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(`build_format` / the `..$args` pack). Compare the IR for the inline vs
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imported-module versions (`sx ir` on each) — the diff at the `xx i` arg site
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is the lead.
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- `src/ir/emit_llvm.zig`: `.box_any` (≈ line 3258) — `coerceToI64` /
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`anyTag(source_type)`. Check whether the imported-module path supplies a
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wrong `source_type` (e.g. `.unresolved` / `.void`) so the tag/width is off.
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Verification: run the reproduction above; expect `[x:\n item 0\n item 1\n]`
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(no segfault). Then re-confirm the auto-box and inline forms still work, and
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that `xx` on a non-Any target (e.g. `xx ptr` to integer) is unaffected.
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Once fixed, ERR E3.3 resumes: restore `library/modules/trace.sx` (the
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`trace.to_string()` / `print_current()` formatter) using the `xx frame` form,
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and complete the E3.3 step (example + snapshot + commit).
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