Three sibling arms of the #10 global-str/slice INDEX miscompile (23670d7,
the READ path) shared the identical N_TARRAY/N_TPTR tnode-KIND whitelist in
their global-ident resolution arm and were still LIVE and silently cs!=ww:
- cgun `&s[1]` / `&g[1]` (cgenexpr.ww N_INDEX addr-of) — a global str
(tnode N_TNAME) / slice (N_TSLICE) matched neither arm, so esz stayed at
the default 8 and the base fell to the complex-base fallback: a wide
{ptr,len,cap} header + 8-byte stride instead of MOVQ name(SB) (.ptr) +
ADDQ.
- cgassign `g[1] = v` store AND `g[1] OP= v` compound (two arms) — same
whitelist; a global slice store emitted a full-word MOVQ at an 8-byte
stride: an 8-BYTE OUT-OF-BOUNDS WRITE past a 1-byte element (memory
corruption) instead of MOVB at .ptr+1.
cstage (cmd/w6c/cgen.c) is the runtime-correct reference and was already
uniform across all three: esz off idx_eff(base->type)->sub->size and the
base load gated by is_arr (TY_ARRAY -> LEAQ name(SB), every other -> MOVQ
name(SB), since a str/slice's .ptr IS the symbol's first word). Align the
wwstage UP to that, mirroring the just-landed cgindex template (#10): resolve
esz via elemsizeofc with no kind gate, dispatch the base by N_TARRAY ? LEAQ :
MOVQ name(SB). The store/compound arms also resolve elemtn exactly like their
local branch (element node for ARRAY/SLICE/PTR; nil for str so tnodestoreop
picks MOVB) so a global []str store routes to the 3-word header store and the
compound arm's str/slice hard-error still fires.
Close-by-construction: the global element base/stride is now computed off the
resolved type at every wwstage index site — read (cgindex, #10), addr-of
(cgun), store + compound (cgassign) — with no remaining tnode-kind whitelist.
cgslice/cgbaselen already resolved via elemsizeofc.
803_globalidx_run extends from 9 to 18 rows: global str/slice addr-of (read
back through the pointer), global slice store AND compound store `g[i] OP= v`
(the distinct third fixed arm, with adjacent-element addends as the OOB-write
guard on both), a WIDTH>1 signed variant of each (esz=4 stride/store-width pin),
and local addr-of/store regression pins. Runtime (cstage build+run) + cs==ww
byte-id per row. combined.ww embeds (w6c + wwdump) regenerate.
Hojun-Cho
a9228dabb3