ww/test/wcc/734_struct_modshadow.c

/*
 * 734_struct_modshadow — sentinel for the trio leaf-name pattern's
 * 5th leaf: wwstage's structlookup. Pins bare-leaf `*S` field access
 * to a same-module-first walk so the load picks the caller's own
 * `S` (correct field offset / totsize) rather than another module's
 * same-leaf-name `S` sitting at the head of c.structs.
 *
 * Pre-fix wwstage's `structlookup` (selfhost/cmd/wcc/cgenutil.ww)
 * walked c.structs head-first by sname, returning the FIRST match.
 * The cgdot `*struct` field-load branch handed it `inner.str` (the
 * bare leaf from a parsed N_TPTR whose inner is N_TNAME) and the
 * head-pick silently emitted the wrong-module field offset — a
 * displacement against BX that loaded whatever the colliding-module
 * struct happened to align there. Silent miscompile, not byte-id:
 * cstage's resolve_typename uses scope_lookup_prefer(cur, cur_mod,
 * leaf) so check.c already binds the correct Type, and cgen.c reads
 * fi.foff off the typed Sym — cs vs ws asm diverged on every bare-
 * leaf collision but no in-tree corpus declares two same-leaf
 * structs, so 995 stayed green and the latent miscompile only
 * surfaces once a stdlib port introduces the collision (same shape
 * as #4a enumlookup surfacing post-strings).
 *
 * Trio's structural close per task #4 leaves: structlookup grows a
 * same-module-first walk before the head-walk fallback, mirroring
 * aliaslookup (#27), fnparamslookupmod (#28), fnretlookupmod (#31)
 * and enumlookup (#4a). NO structlookupmod variant: the consumer
 * surface for `pkg.S` is fully captured by the parser collapsing
 * dotted N_TNAME into a single str with embedded `.`, which routes
 * through structlookup's existing smod==pkg embedded-dot branch.
 * Cstage carries no sister bug — resolve_typename already routes
 * the bare-leaf TY_STRUCT name through scope_lookup_prefer per
 * c->cur_mod (cmd/wcc/check.c:60).
 *
 * Asserts the post-fix field-offset land inside the matching TEXT
 * sym on BOTH stages and that cs vs ws stay byte-identical on each
 * row. Row 1 sentinel-flips this commit's new same-module-first
 * walk (revert the structlookup change → row 1 fails on wwstage
 * + cs-vs-ws diff). Row 2 exercises the pre-existing embedded-dot
 * smod==pkg branch (unchanged here) — defensive coverage that
 * guards the second structlookup path against future regression;
 * does not sentinel-flip on this commit's change.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.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;
	const char *textsym;	/* TEXT sym containing the load */
	const char *want_imm;	/* the displacement that MUST appear */
	const char *bad_imm;	/* the displacement that MUST NOT appear */
};

/* Field layout (registerstruct: 8B alignment for >=8B, 4B for >=4).
 * Offsets chosen so neither digit-string is a substring of the
 * other (12 vs 32) — strstr-based needle matching would otherwise
 * spuriously hit "4(BX)," inside "24(BX),".
 *   beta.S  = { tag1, tag2, tag3, mark: i32 } → mark foff = 12, totsize = 16
 *   alpha.S = { p1, p2, p3, p4: i64, mark: i32 }
 *                                            → mark foff = 32, totsize = 40
 *
 * Source orderings pick which module's S sits at the head of
 * c.structs after collectstructs' head-prepend walk. The LAST `type
 * S = struct ...` in source order ends at the head — that's the
 * leaf-collision the same-module-first walk must beat. */
static const struct row rows[] = {
	{ "bare_leaf_same_module",
	  "package gamma;\n"
	  "import alpha;\n"
	  "import beta;\n"
	  "export fn main() i32 = { return 0; };\n"
	  "package beta;\n"
	  "type S = struct { tag1: i32, tag2: i32, tag3: i32, mark: i32, };\n"
	  "export fn readbetamark(s: *S) i32 = { return s.mark; };\n"
	  "package alpha;\n"
	  "type S = struct { p1: i64, p2: i64, p3: i64, p4: i64, mark: i32, };\n",
	  "TEXT beta.readbetamark", "12(BX),", "32(BX)," },
	/* `alpha.S` collapses into a single N_TNAME str at parse time
	 * (lib/ww/parse/parse.ww joindotted), so structlookup is called
	 * with "alpha.S" and falls through the new same-module-first
	 * walk (no s.sname == "alpha.S") + head walk into the existing
	 * embedded-dot branch (leaf="S", pkg="alpha", filter smod==pkg).
	 * Pre/post-fix both pick alpha — row 2 sentinel-flips ONLY if
	 * the smod==pkg filter regresses, pinning the second lookup
	 * path independent of row 1's same-module-first walk. */
	{ "dot_qualified_explicit_module",
	  "package gamma;\n"
	  "import alpha;\n"
	  "import beta;\n"
	  "export fn main() i32 = { return 0; };\n"
	  "package alpha;\n"
	  "type S = struct { p1: i64, p2: i64, p3: i64, p4: i64, mark: i32, };\n"
	  "export fn readalphamark(s: *alpha.S) i32 = { return s.mark; };\n"
	  "package beta;\n"
	  "type S = struct { tag1: i32, tag2: i32, tag3: i32, mark: i32, };\n",
	  "TEXT alpha.readalphamark", "32(BX),", "12(BX)," },
};

static int
slurp(const char *path, char *buf, size_t cap)
{
	FILE *f = fopen(path, "rb");
	if (!f) return -1;
	size_t n = fread(buf, 1, cap - 1, f);
	fclose(f);
	buf[n] = '\0';
	return (int)n;
}

static int
emit_s(const char *w6c, const struct row *r, int i, char *out_s, size_t cap)
{
	char src[64], cmd[1024];
	snprintf(src, sizeof src, "/tmp/sms_%d_%d.ww", getpid(), i);
	snprintf(out_s, cap, "/tmp/sms_%d_%d_%s.s",
	    getpid(), i, w6c[strlen(w6c) - 1] == 'w' ? "ww" : "c");

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

	snprintf(cmd, sizeof cmd, "%s -o %s %s 2>/dev/null", w6c, out_s, src);
	int rc = runwait(cmd);
	unlink(src);
	return rc;
}

/* Inside the named TEXT sym, before its first RET, the want_imm
 * MUST appear and the bad_imm MUST NOT. bad_imm flags pre-fix
 * head-walk picking the wrong-module S's field offset. */
static int
check_imm(const char *spath, const struct row *r, const char *stage)
{
	char buf[1 << 14];
	if (slurp(spath, buf, sizeof buf) < 0) {
		fprintf(stderr, "row[%s][%s]: cannot read %s\n",
		    r->label, stage, spath);
		return -1;
	}
	const char *fn = strstr(buf, r->textsym);
	if (!fn) {
		fprintf(stderr, "row[%s][%s]: no %s in %s\n",
		    r->label, stage, r->textsym, spath);
		return -1;
	}
	const char *ret = strstr(fn, "\tRET");
	if (!ret) {
		fprintf(stderr, "row[%s][%s]: no RET inside %s\n",
		    r->label, stage, r->textsym);
		return -1;
	}
	const char *good = strstr(fn, r->want_imm);
	if (!good || good >= ret) {
		fprintf(stderr,
		    "row[%s][%s]: want_imm %s missing inside %s\n",
		    r->label, stage, r->want_imm, r->textsym);
		return -1;
	}
	const char *bad = strstr(fn, r->bad_imm);
	if (bad && bad < ret) {
		fprintf(stderr,
		    "row[%s][%s]: bad_imm %s present inside %s — wrong-module S\n",
		    r->label, stage, r->bad_imm, r->textsym);
		return -1;
	}
	return 0;
}

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 w6c[640], w6c_ww[640];
	snprintf(w6c, sizeof w6c, "%s/w6c", bin);
	snprintf(w6c_ww, sizeof w6c_ww, "%s/w6c_ww", bin);

	int have_ww = (access(w6c_ww, X_OK) == 0);
	int n = (int)(sizeof rows / sizeof rows[0]);
	int total = 0, fail = 0;

	for (int i = 0; i < n; i++) {
		char cs_path[128], ws_path[128];

		if (emit_s(w6c, &rows[i], i, cs_path, sizeof cs_path) != 0) {
			fprintf(stderr,
			    "struct_modshadow[cstage][%s]: w6c failed\n",
			    rows[i].label);
			fail++; total++; continue;
		}
		total++;
		if (check_imm(cs_path, &rows[i], "cstage") != 0) fail++;

		if (!have_ww) { unlink(cs_path); continue; }

		if (emit_s(w6c_ww, &rows[i], i, ws_path, sizeof ws_path) != 0) {
			fprintf(stderr,
			    "struct_modshadow[wwstage][%s]: w6c_ww failed\n",
			    rows[i].label);
			fail++; total++;
			unlink(cs_path); continue;
		}
		total++;
		if (check_imm(ws_path, &rows[i], "wwstage") != 0) fail++;

		total++;
		char cmd[512];
		snprintf(cmd, sizeof cmd, "cmp -s %s %s", cs_path, ws_path);
		if (runwait(cmd) != 0) {
			fprintf(stderr,
			    "struct_modshadow[%s]: cstage vs wwstage asm differs\n",
			    rows[i].label);
			fail++;
		}

		unlink(cs_path); unlink(ws_path);
	}

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