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wwstage: make the cgdot alias-peel struct-break module-aware (#223)

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The wwstage cgdot #191 alias-peel loop broke on a name-keyed any-module
structlookup, so a receiver whose alias name collides with a struct of the
same name in ANOTHER module resolved to the foreign struct and fell through to
an undefined `name(SB)` global instead of the field load. The eFinal FLIP
renames io's `vstream` -> `stream`, which collides with memio's `stream`
struct, so io.read/io.write/io.close's `match (s.reader)` emitted
`MOVQ reader(SB), AX` (reader is also a type-alias) -> cs != ww (cstage chases
the nominal TY_NAMED.under pointer chain, module-correct). Gate-blind: on
master both stages emit the same wrong store so byte-id stays green; the FLIP
corpus is the first to put the io-alias/memio-struct collision in one build.

Fix (wwstage-only align-down; cstage is the authority and is untouched): make
the peel's struct-break MODULE-AWARE — break only on a same-module struct (a
genuine struct-value receiver); a same-module alias keeps peeling to its
underlying (io.stream -> *vtable -> the pointer field-load arm); a foreign leaf
keeps the prior any-module heuristic. New structsamemod / aliassamemod mirror
the same-module-first pass already in structlookup / aliaslookup. This is not a
naive alias-first reorder (which would reintroduce the mirror collision: a
same-module struct plus a foreign same-leaf alias). Peel-only — the direct-
struct arm's broader cross-module same-leaf-STRUCT name-keying is filed as #224.

#208-family (name-keyed resolution dropping to a wrong global) but in cgen, not
the checker; #213 is distinct (cosmetic local-struct-match divergence).

test/wcc/784_xmod_alias_struct_collide_run: collision (cross-module alias-vs-
struct, same leaf), symmetric (guards the same-module-struct break against a
naive reorder), and a no-collision control — branched callee. The discriminating
net is cs.s == ww.s (the path is gate-blind and cstage is correct, so byte-id
flips when wwstage is fixed); confirmed by source-revert. The FLIP's combined.ww
is now cs.s == ww.s byte-identical.
This commit is contained in:
Hojun-Cho
2026-05-30 02:00:07 +09:00
parent 1175711021
commit 80184a3acf
7 changed files with 528 additions and 9 deletions
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26
selfhost/cmd/wcc/cgenexpr.ww
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@@ -1766,10 +1766,30 @@ fn cgdot(c: *cgen, n: *node) void = {
// builds NAMED chains (project_tinfo_lossy_nominal). Stops
// at struct aliases so the existing direct-struct arm below
// stays byte-id with pre-fix #22 callers. #191.
//
// #223: the break is MODULE-AWARE. cstage type_chase_named
// follows the resolved NAMED.under pointer (module-correct);
// wwstage re-resolves by name (lossy), so a same-module
// alias whose leaf collides with a FOREIGN struct of the
// same name (io.stream = *vtable vs memio.stream struct)
// would wrongly halt the peel at the foreign struct via
// structlookup's any-module fallback → field load drops to a
// bogus `MOVQ <fld>(SB)`. Sibling of #208 (lossy name-keyed
// resolution leaking to a global leaf). Break ONLY on a
// same-module struct (a genuine struct-value receiver); a
// same-module alias keeps peeling; a foreign leaf (in
// neither registry for c.curmod) falls back to the prior
// any-module heuristic. The broader cross-module same-leaf
// STRUCT name-keying at the direct-struct arm below is
// filed separately as #224 (not FLIP-triggered).
for (tn != nil && tn.kind == nkind.N_TNAME) {
if (structlookup(c, tn.str) != nil) { break; };
let nx: *node = aliaslookup(c, tn.str);
if (nx == nil) { break; };
if (structsamemod(c, tn.str) != nil) { break; };
let nx: *node = aliassamemod(c, tn.str);
if (nx == nil) {
if (structlookup(c, tn.str) != nil) { break; };
nx = aliaslookup(c, tn.str);
if (nx == nil) { break; };
};
tn = nx;
};
if (tn == nil) { return; };