ww/test/wcc/938_str_chainfield_store_cap_run.c

/*
 * 938_str_chainfield_store_cap_run — runtime coverage for the G2 fold: STORING a
 * str into a FIELD reached through a *struct-VALUED EXPRESSION (`r.sym.f = v`,
 * the chained-N_DOT store) must write the full 24B {ptr,len,cap} header, not
 * just {ptr,len}. str is 24B since Phase 2 (#1); the chained-store arm
 * previously stored only 2 words (AX=ptr@foff+0, BX=len@foff+8) and silently
 * DROPPED cap — the second STORE-cluster fold, after the arrfield store (937).
 *
 * This is the write-side mirror of the landed chained *struct str-field READ
 * (caseB, #11) and is only meaningful now that read is 3-word: before that the
 * store+read were 2-word-symmetric and cap was untouched at both ends, so a
 * dropped store-cap was invisible. Now the read returns the real +16 word, so a
 * 2-word store is observable.
 *
 * Sites: cgen.c's chained-N_DOT `<expr>.field = v` str branch (n->lhs is N_DOT,
 * n->lhs->lhs is N_DOT/non-IDENT evaluating to a *struct) and the cgenexpr.ww
 * cgassign twin (strict gate: chain root is a LOCAL ident, every dot resolves
 * through a *struct). The mechanic is a direct transfer of G1 (arrfield store):
 * the rhs str leaves AX=ptr/BX=len/CX=cap, all three spilled (PUSHQ CX/BX/AX)
 * across the base-expr eval (which may clobber any register), the resolved
 * *struct ptr staged in DX off the str AX/BX/CX convention (mirroring the
 * s.f=v store), then the full triple stored at foff+0/+8/+16. The base here is
 * a single-word *struct pointer, so it does not contend for the spilled slots.
 *
 * Rows exercise the CHAINED arm at two depths (a direct-field `s.f=` probe would
 * MISS this arm and test the already-3-word IDENT-base path):
 *   A  depth-2  `r.sym.f = v`     (r: outer, outer.sym: *inner, inner.f: str).
 *   B  depth-3  `r.a.b.f = v`     (two pointer hops; deeper base eval clobbers
 *                                  more registers, stressing the spill).
 *
 * RHS cap!=len: each test str is a literal whose .cap is mutated to a value
 * DISTINCT from its len (NOT a bare literal — literals carry cap==len, which
 * would hide a dropped cap; a str sub-slice was rejected too: ww yields cap==len
 * for `buf[0:2]`, equally hiding the drop). cap=8 and len=2 are both nonzero and
 * unequal so a 2-word store that drops cap is detectable.
 *
 * PRE-POISON (cap=5 != 8, both nonzero, != len): before the G2 store under test,
 * all three slot words are seeded with a DIFFERENT str (ptr='q', len=4, cap=5)
 * via the PROVEN already-3-word DIRECT field store (`st.f = q`, the s.f=v
 * oracle, N_IDENT base) — never the G2 chained store itself (if G2 is broken its
 * own poison write would also drop cap, leaving +16 uninit rather than a
 * controlled poison). The pointee is a local struct; the chain's leaf points at
 * it, so the G2 store overwrites the poisoned field. The G2 store then writes
 * the test str (ptr='h', len=2, cap=8). A broken 2-word store never touches +16,
 * so the 3-word read-back observes the poison cap 5, never 8 — deterministic
 * discrimination with no reliance on a stale register.
 *
 * FULL-TRIPLE ASSERT: a register-reallocation slip in the 3-word store could
 * clobber ptr or len while wiring cap, and a cap-only assert would miss it. So
 * each row reads the value back (landed 3-word chained read, caseB) and checks
 * all three words: ptr (first byte through it — 'h'=104), len (2), cap (8). The
 * 2-word store writes ptr/len correctly (they ARE the two words it keeps), so
 * cap is the fail-before discriminator; ptr/len guard the fix.
 *
 * Verified fail-before (stashed the store edit on BOTH stages → all rows exit 1,
 * cap reads the poison 5) / pass-after (exit 0), both the cstage `ww` and
 * wwstage `ww_ww` drivers.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/wait.h>

static int
runwait(const char *cmd)
{
	int rc = system(cmd);
	if (rc == -1) return -1;
	if (WIFEXITED(rc)) return WEXITSTATUS(rc);
	return -1;
}

struct row { const char *label; const char *src; int want; };

static const struct row rows[] = {
	/* A — depth-2 `r.sym.f = v`. r is a local outer; r.sym is a *inner
	 * pointing at a local struct st. Poison st.f (cap=5,len=4,'q') via the
	 * DIRECT s.f=v 3-word store; then the G2 chained store lands the test
	 * str (cap=8,len=2,'h') through r.sym. */
	{ "chainfield_store_depth2",
	  "type inner = struct { f: str };\n"
	  "type outer = struct { sym: *inner };\n"
	  "export fn main() i32 = {\n"
	  "    let q: str = \"qqqq\"; q.cap = 5i32;\n"
	  "    let p: str = \"hi\";   p.cap = 8i32;\n"
	  "    let st: inner;\n"
	  "    st.f = q;\n"
	  "    let r: outer;\n"
	  "    r.sym = &st;\n"
	  "    r.sym.f = p;\n"
	  "    let s: str = r.sym.f;\n"
	  "    if (s.cap: i32 != 8) { return 1; };\n"
	  "    if (s.len: i32 != 2) { return 2; };\n"
	  "    if (s[0] != 104u8) { return 3; };\n"
	  "    return 0;\n"
	  "};\n",
	  0 },
	/* B — depth-3 `r.a.b.f = v`. Two pointer hops (r.a: *mid, mid.b:
	 * *inner). Poison the leaf via the DIRECT store (`leaf.f = q`); the G2
	 * chained store derefs r.a then .b and overwrites leaf.f. The deeper
	 * base eval clobbers more registers, confirming the spilled triple
	 * survives an arbitrary base-formation. */
	{ "chainfield_store_depth3",
	  "type inner = struct { f: str };\n"
	  "type mid = struct { b: *inner };\n"
	  "type outer = struct { a: *mid };\n"
	  "export fn main() i32 = {\n"
	  "    let q: str = \"qqqq\"; q.cap = 5i32;\n"
	  "    let p: str = \"hi\";   p.cap = 8i32;\n"
	  "    let leaf: inner;\n"
	  "    leaf.f = q;\n"
	  "    let m: mid;\n"
	  "    m.b = &leaf;\n"
	  "    let r: outer;\n"
	  "    r.a = &m;\n"
	  "    r.a.b.f = p;\n"
	  "    let s: str = r.a.b.f;\n"
	  "    if (s.cap: i32 != 8) { return 1; };\n"
	  "    if (s.len: i32 != 2) { return 2; };\n"
	  "    if (s[0] != 104u8) { return 3; };\n"
	  "    return 0;\n"
	  "};\n",
	  0 },
};

static int
run_driver(const char *driver, const struct row *r, int i)
{
	char src[96], tmpdir[96], cmd[1024];
	snprintf(src, sizeof src, "/tmp/strchainfieldstore_%d_%d.ww", getpid(), i);
	snprintf(tmpdir, sizeof tmpdir, "/tmp/strchainfieldstore_%d_d_%d", getpid(), i);

	FILE *f = fopen(src, "wb");
	if (!f) return -1;
	fputs(r->src, f);
	fclose(f);

	mkdir(tmpdir, 0755);
	snprintf(cmd, sizeof cmd, "cd %s && %s build %s",
	    tmpdir, driver, src);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "row[%s]: build via %s failed\n",
		    r->label, driver);
		unlink(src); rmdir(tmpdir);
		return -1;
	}

	const char *base = strrchr(src, '/');
	base = base ? base + 1 : src;
	char outbin[160];
	snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
	char *dot = strrchr(outbin, '.');
	if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
	int got = runwait(outbin);

	unlink(src); unlink(outbin); rmdir(tmpdir);
	return got;
}

int
main(void)
{
	const char *bin = getenv("BIN");
	if (!bin) bin = "out/bin";
	char absbin[512];
	if (bin[0] != '/') {
		char cwd[256];
		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
		bin = absbin;
	}

	char cdrv[640];
	snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
	char wdrv[640];
	snprintf(wdrv, sizeof wdrv, "%s/ww_ww", bin);

	struct { const char *name; const char *path; int gated_on_existence; }
	drivers[] = {
		{ "cstage",  cdrv, 0 },
		{ "wwstage", wdrv, 1 },
		{ NULL, NULL, 0 },
	};

	int n = (int)(sizeof rows / sizeof rows[0]);
	int total = 0, fail = 0;
	for (int d = 0; drivers[d].name; d++) {
		if (drivers[d].gated_on_existence
		    && access(drivers[d].path, X_OK) != 0) {
			fprintf(stderr,
			    "str_chainfield_store_cap_run: skip %s (no %s)\n",
			    drivers[d].name, drivers[d].path);
			continue;
		}
		for (int i = 0; i < n; i++) {
			int got = run_driver(drivers[d].path, &rows[i], i);
			total++;
			if (got != rows[i].want) {
				fprintf(stderr,
				    "str_chainfield_store_cap_run[%s][%s]: exit=%d want=%d\n",
				    drivers[d].name, rows[i].label,
				    got, rows[i].want);
				fail++;
			}
		}
	}

	if (fail) {
		fprintf(stderr, "str_chainfield_store_cap_run: %d/%d fixtures failed\n",
		    fail, total);
		return 1;
	}
	printf("str_chainfield_store_cap_run: %d/%d ok\n", total, total);
	return 0;
}