ww/test/wcc/989_structlocal_frame.c

/*
 * 989_structlocal_frame (#75) — a struct LOCAL's stack slot must be the
 * struct's NATURAL size rounded to the 8B grain, identically in both
 * stages. wwstage's slotsize() TY_STRUCT arm (selfhost/cmd/wcc/
 * cgenutil.ww) returned ti.slotsize — the SUM of the slot-padded field
 * widths — so a sub-8 nested-composite struct local over-reserved: a
 * nested inner{x:u8,y:u8} (size 2, slotsize 8) padded its in-struct
 * footprint, and the local's frame slot inherited that pad. cstage has
 * no slotsize SSoT — it reserves the local at f->type->size, the
 * checker's NATURAL r.size (cmd/w6c/cgen.c). So on outer{a:u8,
 * p:inner{x:u8,y:u8}, z:i64} ww emitted frame $32 / struct-base -24(BP)
 * while cstage emitted $16 / -16(BP): a uniform -8 BP shift on every
 * field access. Both stages exit 0 (each self-consistent), so it is
 * runtime-invisible — but it is a cs!=ww .s divergence (rule 10) and a
 * latent byte-id gate-landmine the day such a struct enters the corpus.
 * Same dual-SSoT leak as #44 (field-OFFSET) / #55, one notion over:
 * struct-local-slot-SIZE.
 *
 * THE FIX: slotsize()'s TY_STRUCT arm returns round8(ti.size). The
 * TUPLE arm (8B/elem slot, user ruling #60) and ARRAY arm (element
 * stride, #48) keep ti.slotsize — deliberate, ruled divergences.
 *
 * This is the FRAME-ABSOLUTE proof: each fixture is compiled through
 * cstage w6c AND wwstage w6c_ww and the emitted .s is byte-diffed (the
 * 683 asm_byte_identical pattern). Byte-identity subsumes the frame:
 * pre-fix nested3 differs at `TEXT main,$32` vs `$16`, `SUBQ $32` vs
 * `$16`, and every `-24(BP)` vs `-16(BP)`; post-fix the two .s are
 * byte-for-byte equal. The sibling RUNTIME exit-code proof migrated to
 * test/lang/nestfield_test.ww (@test field-read rows, cs==ww via the T2
 * byte-id gate); this file is the .s/frame-absolute one #75 owes.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.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; };

static const struct row rows[] = {
	/* nested3 — the core divergence. outer{a:u8, p:inner{x:u8,y:u8},
	 * z:i64}: natural size 16 (a@0, p@1 packed, z@8), slot-padded sum 24
	 * (a:8 + p:8 + z:8). Pre-fix ww frame $32 / base -24(BP); cstage
	 * $16 / -16(BP). The successor z makes the -8 shift visible on a
	 * wide field too. */
	{ "nested3",
	  "package main;\n"
	  "type inner = struct { x: u8, y: u8 };\n"
	  "type outer = struct { a: u8, p: inner, z: i64 };\n"
	  "export fn main() int = {\n"
	  "	let o: outer = outer { a = 1, p = inner { x = 2, y = 3 },"
	  " z = 0x44444444i64 };\n"
	  "	if (o.a: int != 1) { return 1; };\n"
	  "	if (o.p.x: int != 2) { return 2; };\n"
	  "	if (o.p.y: int != 3) { return 3; };\n"
	  "	if (o.z != 0x44444444i64) { return 4; };\n"
	  "	return 0;\n"
	  "};\n" },

	/* tail-varied — same sub-8 nested composite, a narrower (u32) tail.
	 * outt{a:u8, p:inner{x:u8,y:u8}, w:u32}: natural size 8 (w@4),
	 * slot-padded sum larger. Proves the fix on a second sub-8 shape
	 * whose natural size differs from nested3's. */
	{ "tail_u32",
	  "package main;\n"
	  "type inner = struct { x: u8, y: u8 };\n"
	  "type outt = struct { a: u8, p: inner, w: u32 };\n"
	  "export fn main() int = {\n"
	  "	let o: outt = outt { a = 1, p = inner { x = 2, y = 3 },"
	  " w = 0x1234u32 };\n"
	  "	if (o.p.y: int != 3) { return 3; };\n"
	  "	if (o.w != 0x1234u32) { return 5; };\n"
	  "	return 0;\n"
	  "};\n" },

	/* flat control — flat{a:u8, b:i64}, no sub-8 composite field.
	 * Natural and slot-padded coincide (b@8 either way), so the .s is
	 * byte-id BEFORE and after; proves the fix leaves the common case
	 * unmoved (no spurious frame change on plain structs). */
	{ "flat_ctl",
	  "package main;\n"
	  "type flat = struct { a: u8, b: i64 };\n"
	  "export fn main() int = {\n"
	  "	let o: flat = flat { a = 9, b = 0x33333333i64 };\n"
	  "	if (o.a: int != 9) { return 1; };\n"
	  "	if (o.b != 0x33333333i64) { return 2; };\n"
	  "	return 0;\n"
	  "};\n" },
};

/* asm_byte_identical — emit .s via cstage w6c and wwstage w6c_ww and
 * diff (the 683_arr_strslice_elem harness). Pre-#75 a sub-8 nested
 * struct local over-reserved its frame slot on wwstage, so the .s
 * diverged (frame size, SUBQ, every field BP offset); the natural-size
 * slot makes the two byte-for-byte equal. */
static int
asm_byte_identical(const char *bin, const struct row *r, int i)
{
	char src[64], cs[64], ws[64], cmd[1024];
	snprintf(src, sizeof src, "/tmp/slfr_%d_%d.ww", getpid(), i);
	snprintf(cs,  sizeof cs,  "/tmp/slfr_%d_%d_c.s", getpid(), i);
	snprintf(ws,  sizeof ws,  "/tmp/slfr_%d_%d_w.s", getpid(), i);

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

	snprintf(cmd, sizeof cmd, "%s/w6c -o %s %s 2>/dev/null", bin, cs, src);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "structlocal_frame[%s]: w6c errored\n", r->label);
		unlink(src);
		return -1;
	}
	snprintf(cmd, sizeof cmd, "%s/w6c_ww -o %s %s 2>/dev/null",
	    bin, ws, src);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "structlocal_frame[%s]: w6c_ww errored\n",
		    r->label);
		unlink(src); unlink(cs);
		return -1;
	}

	FILE *fc = fopen(cs, "rb");
	FILE *fw = fopen(ws, "rb");
	int rc = 0;
	if (!fc || !fw) {
		rc = -1;
	} else {
		for (;;) {
			int a = fgetc(fc);
			int b = fgetc(fw);
			if (a != b) { rc = -1; break; }
			if (a == EOF) break;
		}
	}
	if (fc) fclose(fc);
	if (fw) fclose(fw);
	if (rc != 0)
		fprintf(stderr, "structlocal_frame[%s]: cstage vs wwstage "
		    "asm differs (#75 struct-local frame)\n", r->label);
	unlink(src); unlink(cs); unlink(ws);
	return rc;
}

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 wdrv[1024];
	snprintf(wdrv, sizeof wdrv, "%s/w6c_ww", bin);
	if (access(wdrv, X_OK) != 0) {
		fprintf(stderr, "structlocal_frame: skip (no %s)\n", wdrv);
		printf("structlocal_frame: skipped (no wwstage)\n");
		return 0;
	}

	int n = (int)(sizeof rows / sizeof rows[0]);
	int total = 0, fail = 0;
	for (int i = 0; i < n; i++) {
		total++;
		if (asm_byte_identical(bin, &rows[i], i) != 0)
			fail++;
	}

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