ww/test/wcc/934_str_chained_field_cap_run.c

/*
 * 934_str_chained_field_cap_run — runtime coverage for the C4.6-caseB fold:
 * 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}. 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.
 *
 * This is the chained sibling of 933 (which covered the direct / single-deref
 * S1/S2 arms). The site is cgen.c's "Chained N_DOT through a *struct field"
 * branch (n->lhs is itself an N_DOT typed *struct): the lhs cgexpr leaves AX =
 * the inner *struct pointer, then the field is read off AX. caseB folds the
 * str arm onto the adjacent 3-word slice arm — cap loads from +16(AX) and the
 * base (AX = ptr) is read LAST so the earlier index loads still see the base.
 *
 * The byte-id gates (990-997) can't catch a symmetric 2-word miscompile: if
 * both stages drop cap identically, byte-id passes silently. So this pins the
 * *runtime* contract — build through both the cstage `ww` and wwstage `ww_ww`
 * driver and confirm the assertion holds (exit 0).
 *
 * DISCRIMINATION (heed the 933 lesson): 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 call between the field store and the chained read;
 * a call clobbers caller-saved CX (spoil's own str copy leaves cap=44 in CX),
 * so a broken 2-word read observes cap=44, not 8, and the row fails (return 1).
 * Verified fail-before (reverted fold: exit 1) / pass-after (exit 0), both
 * 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[] = {
	/* caseB — `o.p.f` chained read: o a struct holding p: *inr, inr
	 * holding a str field f. Base AX = the inner *struct pointer; the
	 * str field is read 3-word off AX (cap at +16). Poison cap=8
	 * (len=2). spoil() interposes a CX-clobbering call between the
	 * `ist.f = p` store and the chained `o.p.f` read so a broken
	 * 2-word read cannot coincidentally pass on a stale CX. */
	{ "caseb_chained_field",
	  "type inr = struct { f: str };\n"
	  "type otr = struct { p: *inr };\n"
	  "fn spoil() i32 = {\n"
	  "    let z: str = \"zzzz\";\n"
	  "    z.cap = 44i32;\n"
	  "    let w: str = z;\n"
	  "    return w.cap: i32;\n"
	  "};\n"
	  "export fn main() i32 = {\n"
	  "    let p: str = \"hi\";\n"
	  "    p.cap = 8i32;\n"
	  "    let ist: inr;\n"
	  "    ist.f = p;\n"
	  "    let o: otr;\n"
	  "    o.p = &ist;\n"
	  "    let junk: i32 = spoil();\n"
	  "    let s: str = o.p.f;\n"
	  "    if (s.cap: i32 != 8) { return 1; };\n"
	  "    if (s.len: i32 != 2) { return 2; };\n"
	  "    if (junk != 44) { 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/strchainfieldcap_%d_%d.ww", getpid(), i);
	snprintf(tmpdir, sizeof tmpdir, "/tmp/strchainfieldcap_%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_chained_field_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_chained_field_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_chained_field_cap_run: %d/%d fixtures failed\n",
		    fail, total);
		return 1;
	}
	printf("str_chained_field_cap_run: %d/%d ok\n", total, total);
	return 0;
}