ww/test/wcc/989_structcopytail_run.c

/*
 * 989_structcopytail_run — #73 teeth (recorded by impl-55, 2026-06-13).
 *
 * Whole-struct field-copy ragged tail. A `x.i = o` copy of a struct whose
 * NATURAL size is not 8-aligned must move exactly that many bytes via a
 * descending-greedy 8->4->2->1 tail (MOVL/MOVW/MOVB), NOT round up to an
 * 8-byte MOVQ that bleeds into the field's natural-offset successor.
 *
 * THIS TEST IS cs!=ww-RED UNTIL #73. As impl-55 proved (2026-06-13), BOTH
 * stages inline a tail handling only {4,1}; a natural size %8 in
 * {2,3,5,6,7} falls through to an 8-byte MOVQ over-write:
 *   - wwstage: cgenexpr.ww 4 field-copy sites (now length-correct via #71,
 *     tail still 4/1).
 *   - cstage: cmd/w6c/cgen.c:5302/5318 (+ siblings 2970/3332/5268/6255/
 *     6314/7259) — str_fu->size length is already natural, tail is 4/1.
 * ASM PROOF (tail2, x.i = o): cstage emits `MOVQ -8(BP),AX; MOVQ AX,-16(BP)`
 * (8B over-write -> clobbers mark@-12). #73 routes both stages' field copy
 * through the canonical greedy emitter (cstage cg_aggcopy@2241 / ww
 * aggcopy@1662), completing the tail on both -> this test goes green
 * cs==ww. Do NOT wire it before #73 lands.
 *
 * Shapes:
 *   tail2: inner2{a:u8,b:u8} (size 2) in outer2{i:inner2, mark:i32}; #44
 *          packs mark at natural offset 4. A MOVQ copy of i writes [0,8)
 *          and clobbers mark@4; the MOVW tail writes [0,2).
 *   tail6: inner6{a:u16,b:u16,c:u16} (size 6) in outer6{i:inner6, mark:u8};
 *          mark at natural offset 6. A MOVQ copy writes [0,8) and clobbers
 *          mark@6; the MOVL+MOVW tail writes [0,6).
 *   ctl8:  inner8{a:i64} (size 8, 8-aligned) — the MOVQ loop alone, no
 *          tail; proves the 8-aligned path is unchanged.
 * Each program reads every field back and returns the 1-based index of the
 * first mismatch, 0 on all-correct. Both stages build+run (rule-10), pin 0.
 */
#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_exit;	/* >= 0: pin the absolute value; -1: cs==ww only */
};

static const struct row rows[] = {
	/* tail2 — whole-copy of a 2-byte struct; mark (nat offset 4) must
	 * survive. Pre-tail-fix MOVQ writes [0,8) -> mark clobbered. */
	{ "tail2",
	  "package main;\n"
	  "type inner2 = struct { a: u8, b: u8 };\n"
	  "type outer2 = struct { i: inner2, mark: i32 };\n"
	  "export fn main() int = {\n"
	  "	let o: inner2 = inner2 { a = 0x11, b = 0x22 };\n"
	  "	let x: outer2;\n"
	  "	x.mark = 0x7f7f7f7f;\n"
	  "	x.i = o;\n"
	  "	if (x.i.a: int != 0x11) { return 1; };\n"
	  "	if (x.i.b: int != 0x22) { return 2; };\n"
	  "	if (x.mark != 0x7f7f7f7f) { return 3; };\n"
	  "	return 0;\n"
	  "};\n",
	  0 },

	/* tail6 — whole-copy of a 6-byte struct; mark:u8 (nat offset 6) must
	 * survive. Pre-tail-fix MOVQ writes [0,8) -> mark clobbered; the
	 * MOVL+MOVW tail writes exactly [0,6). */
	{ "tail6",
	  "package main;\n"
	  "type inner6 = struct { a: u16, b: u16, c: u16 };\n"
	  "type outer6 = struct { i: inner6, mark: u8 };\n"
	  "export fn main() int = {\n"
	  "	let o: inner6 = inner6 { a = 0x1111, b = 0x2222, c = 0x3333 };\n"
	  "	let x: outer6;\n"
	  "	x.mark = 0x5a;\n"
	  "	x.i = o;\n"
	  "	if (x.i.a: int != 0x1111) { return 1; };\n"
	  "	if (x.i.b: int != 0x2222) { return 2; };\n"
	  "	if (x.i.c: int != 0x3333) { return 3; };\n"
	  "	if (x.mark: int != 0x5a) { return 4; };\n"
	  "	return 0;\n"
	  "};\n",
	  0 },

	/* tail7 — whole-copy of a 7-byte struct (seven u8, align 1); mark:u8
	 * at natural offset 7 must survive. Exercises the FULL descending tail
	 * ladder in one shape: MOVL[0,4) + MOVW[4,6) + MOVB[6,7). Pre-fix the
	 * 4/1-only tail defaulted size-7 to a single 8-byte MOVQ writing [0,8)
	 * -> clobbers mark@7; this is the only row hitting the MOVB tail. */
	{ "tail7",
	  "package main;\n"
	  "type inner7 = struct { a: u8, b: u8, c: u8, d: u8, e: u8, f: u8, g: u8 };\n"
	  "type outer7 = struct { i: inner7, mark: u8 };\n"
	  "export fn main() int = {\n"
	  "	let o: inner7 = inner7 { a = 0x11, b = 0x22, c = 0x33, d = 0x44, e = 0x55, f = 0x66, g = 0x77 };\n"
	  "	let x: outer7;\n"
	  "	x.mark = 0x5a;\n"
	  "	x.i = o;\n"
	  "	if (x.i.a: int != 0x11) { return 1; };\n"
	  "	if (x.i.b: int != 0x22) { return 2; };\n"
	  "	if (x.i.c: int != 0x33) { return 3; };\n"
	  "	if (x.i.d: int != 0x44) { return 4; };\n"
	  "	if (x.i.e: int != 0x55) { return 5; };\n"
	  "	if (x.i.f: int != 0x66) { return 6; };\n"
	  "	if (x.i.g: int != 0x77) { return 7; };\n"
	  "	if (x.mark: int != 0x5a) { return 8; };\n"
	  "	return 0;\n"
	  "};\n",
	  0 },

	/* ctl8 — 8-aligned struct: the MOVQ loop alone, zero tail iterations.
	 * Proves the 8-aligned emission path stays correct (byte-id caveat). */
	{ "ctl8",
	  "package main;\n"
	  "type inner8 = struct { a: i64 };\n"
	  "type outer8 = struct { i: inner8, mark: i64 };\n"
	  "export fn main() int = {\n"
	  "	let o: inner8 = inner8 { a = 0x1234567 };\n"
	  "	let x: outer8;\n"
	  "	x.mark = 0x76543210;\n"
	  "	x.i = o;\n"
	  "	if (x.i.a != 0x1234567) { return 1; };\n"
	  "	if (x.mark != 0x76543210) { return 2; };\n"
	  "	return 0;\n"
	  "};\n",
	  0 },
};

/* run_build — build+run `src` via `driver`; returns the binary's exit
 * code, or -1 on a build failure. */
static int
run_build(const char *driver, const struct row *r, int i)
{
	char src[64], tmpdir[64], cmd[1024];
	snprintf(src, sizeof src, "/tmp/sctail_%d_%d.ww", getpid(), i);
	snprintf(tmpdir, sizeof tmpdir, "/tmp/sctail_%d_d_%d", getpid(), i);

	FILE *f = fopen(src, "wb");
	if (!f) return -2;
	fputs(r->src, f);
	fclose(f);

	mkdir(tmpdir, 0755);
	snprintf(cmd, sizeof cmd, "cd %s && %s build %s 2>/dev/null",
	    tmpdir, driver, src);
	int brc = runwait(cmd);

	const char *base = strrchr(src, '/');
	base = base ? base + 1 : src;
	char outbin[128];
	snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
	char *dot = strrchr(outbin, '.');
	if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';

	int got = -1;
	if (brc == 0) got = runwait(outbin);

	unlink(src); unlink(outbin); rmdir(tmpdir);
	return brc == 0 ? got : -1;
}

int
main(void)
{
	const char *bin = getenv("BIN");
	if (!bin) bin = "out/bin";
	char absbin[1024];
	if (bin[0] != '/') {
		char cwd[1024];
		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
		bin = absbin;
	}

	char cdrv[1024], wdrv[1024];
	snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
	snprintf(wdrv, sizeof wdrv, "%s/ww_ww", bin);
	int have_ww = (access(wdrv, X_OK) == 0);

	int n = (int)(sizeof rows / sizeof rows[0]);
	int total = 0, fail = 0;

	for (int i = 0; i < n; i++) {
		total++;
		int gc = run_build(cdrv, &rows[i], i);
		if (gc < 0) {
			fprintf(stderr, "structcopytail_run[cstage][%s]: build/run "
			    "failed (got %d)\n", rows[i].label, gc);
			fail++;
			continue;
		}
		if (rows[i].want_exit >= 0 && gc != rows[i].want_exit) {
			fprintf(stderr, "structcopytail_run[cstage][%s]: exit=%d "
			    "want=%d (field/clobber mismatch)\n",
			    rows[i].label, gc, rows[i].want_exit);
			fail++;
		}
		if (!have_ww) {
			fprintf(stderr, "structcopytail_run: skip wwstage (no %s)\n",
			    wdrv);
			continue;
		}
		int gw = run_build(wdrv, &rows[i], i);
		if (gw != gc) {
			fprintf(stderr, "structcopytail_run[%s]: cs=%d != ww=%d "
			    "(copy-tail divergence — #71)\n",
			    rows[i].label, gc, gw);
			fail++;
		}
		if (rows[i].want_exit >= 0 && gw != rows[i].want_exit) {
			fprintf(stderr, "structcopytail_run[wwstage][%s]: exit=%d "
			    "want=%d (field/clobber mismatch)\n",
			    rows[i].label, gw, rows[i].want_exit);
			fail++;
		}
	}

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