ww/test/wcc/688_global_arr_elem_field.c

/*
 * 688_global_arr_elem_field — a module-GLOBAL indexed struct-element
 * `.field` READ (`g[i].field`, g at module scope) lowers the field
 * offset, not just the element stride. The READ twin of #11 (which
 * fixed the global `g[i] = v` WRITE) and the #15 sibling.
 *
 * Pre-fix (#21): the `arr[i].field` N_DOT branch in both stages was
 * gated on a LOCAL lookup (cstage localfind != 0, wwstage
 * localfindnode != nil). A module-global base missed it and fell
 * through — cstage to a generic index-load that drops f->offset
 * (reads element[i] at offset 0, so g[0].b returned a's value), and
 * wwstage to the module-qualified fallback (garbage — no g load).
 * Byte-id-divergent silent miscompile.
 *
 * The fix (BOTH stages, converged byte-identical): resolve the global
 * the same way the N_INDEX arm does (cstage let_islet || def_isarraydef;
 * wwstage letvartnode || defvartnode) and dispatch the base load by
 * shape — array -> LEAQ name(SB) (the symbol IS the storage),
 * slice/ptr -> MOVQ name(SB) (the symbol's first word IS the .ptr) —
 * then load the field at f->offset, exactly as the local arm does.
 * esz = element stride and f->offset both come from the type table.
 *
 * Coverage:
 *   arr_a0/a1   | [2]pt struct array, g[0].a / g[1].a — control,
 *               | offset 0. RUNTIME + byte-id.
 *   arr_b0/b1   | [2]pt, g[0].b / g[1].b — THE bug (offset 8, the
 *               | reads that returned a's value pre-fix). RUNTIME.
 *   rec_*       | [2]rec { tag:u8, x:i32, y:i64 } — non-8-aligned
 *               | fields (x@4, y@8) + a u8 sub-word leaf, to stress
 *               | f->offset and the load-width path. RUNTIME.
 *   slice_x1    | [2]rec backing + `let g: []rec = arr;`, g[1].x
 *               | read. Exercises the slice-base MOVQ-deref arm
 *               | (MOVQ g(SB),BX loads .ptr) — the asm is byte-id and
 *               | correct, but a slice-of-struct module global does
 *               | not data-emit a symbol yet (a separate, pre-existing
 *               | data-emission gap, sibling of #10/#20), so it cannot
 *               | LINK/run. Asserted byte-id ONLY; filed separately.
 *
 * Why this was never caught: 680/681 cover only LOCAL `[N]struct`
 * bases (BP-relative). The global base routes through name(SB) and was
 * a distinct, untested arm.
 *
 * Cstage and wwstage each on every runtime fixture; wwstage gated on
 * access(X_OK). All fixtures additionally asm-byte-id checked.
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/wait.h>

/* want == BYTEID_ONLY: the row cannot LINK/run (a slice-of-struct
 * module global does not data-emit yet — separate gap), so only the
 * cstage/wwstage asm-byte-id is asserted, never an exit value. */
#define BYTEID_ONLY (-2147483647 - 1)

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[] = {
	/* [2]pt, .a field at offset 0 — control. */
	{ "arr_a0",
	  "type pt = struct { a: i64, b: i64 };\n"
	  "let g: [2]pt = [pt { a = 1, b = 2 }, pt { a = 3, b = 4 }];\n"
	  "export fn main() i32 = { return g[0].a: i32; };\n",
	  1 },
	{ "arr_a1",
	  "type pt = struct { a: i64, b: i64 };\n"
	  "let g: [2]pt = [pt { a = 1, b = 2 }, pt { a = 3, b = 4 }];\n"
	  "export fn main() i32 = { return g[1].a: i32; };\n",
	  3 },
	/* [2]pt, .b at offset 8 — THE bug: pre-fix g[i].b returned a's
	 * value (cstage) or garbage (wwstage). */
	{ "arr_b0",
	  "type pt = struct { a: i64, b: i64 };\n"
	  "let g: [2]pt = [pt { a = 1, b = 2 }, pt { a = 3, b = 4 }];\n"
	  "export fn main() i32 = { return g[0].b: i32; };\n",
	  2 },
	{ "arr_b1",
	  "type pt = struct { a: i64, b: i64 };\n"
	  "let g: [2]pt = [pt { a = 1, b = 2 }, pt { a = 3, b = 4 }];\n"
	  "export fn main() i32 = { return g[1].b: i32; };\n",
	  4 },
	/* [2]rec, non-8-aligned i32 field (x@4) on the second element —
	 * stresses f->offset combined with the element stride. */
	{ "rec_x1",
	  "type rec = struct { tag: u8, x: i32, y: i64 };\n"
	  "let g: [2]rec = [rec { tag = 1u8, x = 100, y = 11 },"
	  " rec { tag = 2u8, x = 200, y = 22 }];\n"
	  "export fn main() i32 = { return g[1].x: i32; };\n",
	  200 },
	/* [2]rec, i64 field (y@8) on the second element. */
	{ "rec_y1",
	  "type rec = struct { tag: u8, x: i32, y: i64 };\n"
	  "let g: [2]rec = [rec { tag = 1u8, x = 100, y = 11 },"
	  " rec { tag = 2u8, x = 200, y = 22 }];\n"
	  "export fn main() i32 = { return g[1].y: i32; };\n",
	  22 },
	/* [2]rec, u8 leaf (tag@0) — sub-word zero-extend load on a
	 * global element base. */
	{ "rec_tag1",
	  "type rec = struct { tag: u8, x: i32, y: i64 };\n"
	  "let g: [2]rec = [rec { tag = 1u8, x = 100, y = 11 },"
	  " rec { tag = 2u8, x = 200, y = 22 }];\n"
	  "export fn main() i32 = { return g[1].tag: i32; };\n",
	  2 },
	/* slice-base MOVQ-deref arm: `let g: []rec = arr;`, g[1].b read.
	 * Byte-id only — a slice-of-struct module global does not
	 * data-emit yet (separate gap), so it cannot link/run. The .s
	 * holds MOVQ g(SB),BX (the .ptr load) + the correct f->offset on
	 * both stages. */
	{ "slice_x1",
	  "type rec = struct { tag: u8, x: i32, y: i64 };\n"
	  "let arr: [2]rec = [rec { tag = 1u8, x = 100, y = 11 },"
	  " rec { tag = 2u8, x = 200, y = 22 }];\n"
	  "let g: []rec = arr;\n"
	  "export fn main() i32 = { return g[1].x: i32; };\n",
	  BYTEID_ONLY },
};

static int
run_driver(const char *driver, const struct row *r, int i)
{
	char tmpdir[64], src[128], outbin[128], rmcmd[160], cmd[1024];
	snprintf(tmpdir, sizeof tmpdir, "/tmp/gae_%d_d_%d", getpid(), i);
	mkdir(tmpdir, 0755);
	snprintf(src,    sizeof src,    "%s/gae_%d_%d.ww", tmpdir, getpid(), i);
	snprintf(outbin, sizeof outbin, "%s/gae_%d_%d",    tmpdir, getpid(), i);
	snprintf(rmcmd,  sizeof rmcmd,  "rm -rf %s", tmpdir);

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

	snprintf(cmd, sizeof cmd, "%s build -o %s %s 2>/dev/null",
	    driver, outbin, src);
	if (runwait(cmd) != 0) {
		fprintf(stderr, "row[%s]: build via %s failed\n",
		    r->label, driver);
		runwait(rmcmd);
		return -1;
	}

	int got = runwait(outbin);

	runwait(rmcmd);
	return got;
}

/* asm_byte_identical — generate .s via cstage's w6c and wwstage's
 * w6c_ww and diff. Pins rule-10 convergence: pre-fix the global-base
 * read diverged (cstage dropped f->offset, wwstage emitted no g load). */
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/gae_asm_%d_%d.ww", getpid(), i);
	snprintf(cs,  sizeof cs,  "/tmp/gae_asm_%d_%d_c.s", getpid(), i);
	snprintf(ws,  sizeof ws,  "/tmp/gae_asm_%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, "row[%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, "row[%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, "row[%s]: cstage vs wwstage asm differs\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 cdrv[1024];
	snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
	char wdrv[1024];
	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, "global_arr_elem_field: skip %s (no %s)\n",
			    drivers[d].name, drivers[d].path);
			continue;
		}
		for (int i = 0; i < n; i++) {
			if (rows[i].want == BYTEID_ONLY)
				continue;	/* byte-id only below */
			int got = run_driver(drivers[d].path, &rows[i], i);
			total++;
			if (got != rows[i].want) {
				fprintf(stderr,
				    "global_arr_elem_field[%s][%s]: exit=%d want=%d\n",
				    drivers[d].name, rows[i].label,
				    got, rows[i].want);
				fail++;
			}
		}
	}

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

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