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ww/test/lang/str_chained_field_cap_test.ww
Hojun-Cho e1740fff10 test: migrate 933-939 str-cap family to test/lang @test
Fan out the str-cap read (933-936) and store (937-939) families into in-language @test files, following the 932 str_elem_cap template. Additive: the *_run.c stay in the C corpus (they are the only wwstage-runtime net for these cs==ww byte-id-blind shapes); de-dup deferred to fold 6.

Per-shape @test fns, not a data table: each fn varies the codegen shape (base reg / chain depth / tuple return-ABI / store position), so the row-array idiom (blocked by #111) would lose coverage. Read family keeps the spoil()/register-clobber + junk==44 discrimination where the .c has it; store family pre-poisons the slot via a path distinct from the store under test. Asserts are primitives only.
2026-06-22 03:54:54 +09:00

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// str_chained_field_cap_test — a CHAINED str-field read `o.p.f` (depth >= 2,
// where p is a *struct field of o and f is a str field of *p) must load the
// full 24B {ptr,len,cap} header, not just {ptr,len}, migrated from
// test/wcc/934_str_chained_field_cap_run.c (C4.6 case B). str is 24B since
// Phase 2 (#1); pre-caseB the chained *struct N_DOT str arm loaded 2 words (ptr
// in AX, len in BX) and dropped cap. The miscompile was cs==ww, so the 990-997
// byte-id gates stayed GREEN while the runtime was wrong — behavioral @test is
// the net. This is the chained sibling of str_field_cap_test (direct/single-
// deref S1/S2): the lhs cgexpr leaves AX = the inner *struct pointer, then the
// field is read off AX, cap from +16(AX), base (AX = ptr) read LAST.
//
// DISCRIMINATION: a 2-word read leaves CX untouched, so the row could
// coincidentally pass if CX happened to still carry the poison cap. spoil()
// interposes a CX-clobbering call between the field store and the chained read
// (its own str copy leaves cap=44 in CX), so a broken read observes 44 not 8.
package str_chained_field_cap_test;
type inr = struct { f: str };
type otr = struct { p: *inr };
fn spoil() i32 = {
let z: str = "zzzz";
z.cap = 44i32;
let w: str = z;
return w.cap: i32;
};
@test fn caseb_chained_field() void = {
// `o.p.f`: o a struct holding p: *inr, inr holding str field f. Poison
// cap=8 (len=2).
let p: str = "hi";
p.cap = 8i32;
let ist: inr;
ist.f = p;
let o: otr;
o.p = &ist;
let junk: i32 = spoil();
let s: str = o.p.f;
assert(s.cap: i32 == 8);
assert(s.len: i32 == 2);
assert(junk == 44);
};