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w6c+w6c_ww: tagged widen-store struct-literal slice field keeps the 3-word header

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The cg_widen_tagged_store / cgwidentaggedstorebp struct-payload arm
gated the 3-word {ptr,len,cap} field store on TY_STR only; a slice-
typed field inside a union-payload struct literal fell to the scalar
tail and silently dropped .len/.cap (the #24 gap's widener twin, both
stages symmetric so byte-id gates were blind). Surfaced by #38's
regex-shaped consumer: wide{xs: []u8, ys: []u8, n} widened into
(wide | error | nomem).
This commit is contained in:
Hojun-Cho
2026-06-04 03:42:15 +09:00
parent 91d42d28ab
commit 5f15eb3d09
4 changed files with 37 additions and 15 deletions
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13
cmd/w6c/cgen.c
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@@ -2343,9 +2343,16 @@ cg_widen_tagged_store(Cg *c, Local **locals_p, Type *dst, Node *src,
}
Type *fu = (ftype && ftype->kind == TY_NAMED)
? ftype->under : ftype;
if (fu && fu->kind == TY_STR) {
/* str IS []u8: 3-word field (ptr,len,cap)
* from cgexpr's AX/BX/CX (#1/Phase 3). */
/* str IS []u8 and a slice is the same 3-word
* {ptr,len,cap} header from cgexpr's AX/BX/CX
* (#1/Phase 3). The slice arm rides #38's
* regex-shaped consumer (slice fields inside a
* union-payload struct literal); the prior
* str-only gate dropped .len/.cap via the
* scalar store below — the #24 gap's widener
* twin. */
if (fu && (fu->kind == TY_STR
|| fu->kind == TY_SLICE)) {
ins2(c, A_MOVQ, areg(D_AX),
amem(D_BP, write_off + 8 + (int)foff + 0));
ins2(c, A_MOVQ, areg(D_BX),