selfhost+cstage+test: graduate deflookup mod-qualified same-module-first (#11)

cstage Sdef walk #2 N_DOT branch used c->cur_mod where n->lhs->str is
the correct module hint. Sister of #4c wwstage graduation; same shape
as the TY_FN branch which already uses mafn(c, n->str, n->lhs->str).

cmd/w6c/cgen.c: add sdef_mod_match_hint(s, hint); walk #2 routes hint
first then head-pick fallback, matching #4a/#28/#31/#34 *mod variant
pattern. selfhost: add deflookuprhsmod(c, name, mod); cgdot N_DOT
mod-qualified str-def value-load routes through it. Rule-10 symmetric
stages: both stages now share the lhs.str polarity (was: both used
cur_mod / cur-module hint).

747_def_modqual_modshadow: table-driven sentinel — gamma calls
alpha.MSG with beta.MSG (same-leaf-name) at head of c.defs/sdefs.
want_imm "$38," (alpha strlit len), bad_imm "$27," (beta strlit len),
plus cs-vs-ws byte-id. Reverting cstage walk #2 to head-pick → fails
$38 on cstage + diverges cs-vs-ws; reverting wwstage cgdot to plain
deflookuprhs → fails $38 on wwstage.

make test 121/121; ww2==ww3==ww4 byte-id holds.

Makefile

@@ -281,6 +281,7 @@ TESTS	= $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
 	  $(BIN)/test_fnret_bare_leaf_shadow \
 	  $(BIN)/test_fnret34_modshadow \
 	  $(BIN)/test_strdef_inline \
+	  $(BIN)/test_def_modqual_modshadow \
 	  $(BIN)/test_param_shadow_mod \
 	  $(BIN)/test_localoff_scope \
 	  $(BIN)/test_cast_enum_movl \
@@ -694,6 +695,10 @@ $(BIN)/test_strdef_inline: test/wcc/746_strdef_inline.c \
 		$(BIN)/w6c $(BIN)/w6c_ww | $(BIN)
 	$(CC) $(CFLAGS) -o $@ $<
 
+$(BIN)/test_def_modqual_modshadow: test/wcc/747_def_modqual_modshadow.c \
+		$(BIN)/w6c $(BIN)/w6c_ww | $(BIN)
+	$(CC) $(CFLAGS) -o $@ $<
+
 $(BIN)/test_match_4arm_cross_module_run: test/wcc/929_match_4arm_cross_module_run.c \
 		$(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
 		$(BIN)/ww_ww $(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \

cmd/w6c/cgen.c

@@ -548,6 +548,20 @@ sdef_mod_match(Cg *c, Sdef *s)
 	return strcmp(a, b) == 0;
 }
 
+/* Explicit-hint variant for `mod.NAME` N_DOT mod-qualified Sdef walks
+ * (sister of wwstage deflookuprhsmod). Walk #2 needs n->lhs->str — a
+ * cross-module qualifier from a third module won't match c->cur_mod
+ * and would fall back to head-pick, possibly inlining the wrong-module
+ * strlit when both source modules export the same-leaf str def. */
+static int
+sdef_mod_match_hint(Sdef *s, const char *hint)
+{
+	const char *a = s->mod;
+	if (a == hint) return 1;
+	if (a == NULL || hint == NULL) return 0;
+	return strcmp(a, hint) == 0;
+}
+
 /* Interned string literals — emitted as DATA directives after all
  * function bodies, so the linker lays them out alongside .text. */
 typedef struct Strlit Strlit;
@@ -5317,14 +5331,36 @@ cgexpr(Cg *c, Node *n, Local *locals)
 				    mafn(c, n->str, n->lhs->str), areg(D_AX));
 				break;
 			}
-			for (Sdef *s = sdefs; s; s = s->next) {
-				if (strcmp(s->name, n->str) != 0) continue;
-				const char *lab = intern_strlit(c, s->bytes,
-				    s->len);
-				ins2(c, A_LEAQ, asym(lab), areg(D_AX));
-				ins2(c, A_MOVQ, aimm((long long)s->len),
-				    areg(D_BX));
-				goto dot_done;
+			{
+				/* Same-module-first walk using n->lhs->str as
+				 * the explicit module hint (sister of wwstage
+				 * deflookuprhsmod). The TY_FN branch above
+				 * already uses n->lhs->str via mafn for the
+				 * cross-module qualifier disambiguation; this
+				 * walk mirrors that polarity so `alpha.MSG`
+				 * from a third module beats a head-of-sdefs
+				 * beta.MSG collision (#11, sister of #4c). */
+				Sdef *s;
+				for (s = sdefs; s; s = s->next) {
+					if (strcmp(s->name, n->str) != 0)
+						continue;
+					if (sdef_mod_match_hint(s, n->lhs->str))
+						break;
+				}
+				if (s == NULL) {
+					for (s = sdefs; s; s = s->next)
+						if (strcmp(s->name, n->str) == 0)
+							break;
+				}
+				if (s != NULL) {
+					const char *lab = intern_strlit(c,
+					    s->bytes, s->len);
+					ins2(c, A_LEAQ, asym(lab), areg(D_AX));
+					ins2(c, A_MOVQ,
+					    aimm((long long)s->len),
+					    areg(D_BX));
+					goto dot_done;
+				}
 			}
 			/* Same gating as the bare-ident catch-all: lets route
 			 * through localloadop (their slot can be the target of

selfhost/cmd/w6c/main.combined.ww

@@ -12673,8 +12673,11 @@ fn cgdot(c: *cgen, n: *node) void = {
 			// strlit-inline matches cstage Sdef walk #2 in
 			// cmd/w6c/cgen.c N_DOT mod-qualified. Without this
 			// the MOVQ leaf(SB) fallback emits a bogus ref
-			// (`alpha.MSG(SB)`, never DATAW-defined). Filed #12.
-			let drhs: *node = deflookuprhs(c, fld);
+			// (`alpha.MSG(SB)`, never DATAW-defined). lhs.str is
+			// the explicit module hint — a 3rd-module qualifier
+			// `alpha.MSG` from gamma needs alpha (not c.curmod)
+			// to beat a head-of-c.defs beta.MSG collision (#11).
+			let drhs: *node = deflookuprhsmod(c, fld, lhs.str);
 			if (drhs != nil) {
 				if (drhs.kind == nkind.N_STRLIT) {
 					let bytes: str = drhs.str;
@@ -20880,6 +20883,29 @@ fn deflookuprhs(c: *cgen, name: str) *node = {
 	return nil;
 };
 
+// deflookuprhsmod — same-module-first walk for `mod.NAME` references.
+// Trio-leaf *mod variant mirroring fnretlookupmod (#31) / fnparamslookupmod
+// (#28) / enumlookupmod (#4a). Module-qualified `alpha.MSG` from a third
+// module needs the explicit alpha hint; deflookuprhs prefers c.curmod
+// (which doesn't match either source module on a 3rd-module qualifier)
+// and falls back to head-pick, possibly inlining beta.MSG's strlit when
+// both alpha and beta declare same-leaf str defs. cgdot's mod-qualified
+// str-def value-load routes here so a cross-module N_DOT collision
+// resolves to the explicit module. Falls back to deflookuprhs's bare-
+// leaf two-pass when no module matches.
+fn deflookuprhsmod(c: *cgen, name: str, mod: str) *node = {
+	if (mod.len > 0) {
+		let e: *defent = c.defs;
+		for (e != nil) {
+			if (streq(e.dname, name)) {
+				if (streq(e.dmod, mod)) { return e.drhs; };
+			};
+			e = e.dnext;
+		};
+	};
+	return deflookuprhs(c, name);
+};
+
 // ---- module-private symbol map --------------------------------------
 //
 // Every non-FFI top-level fn decl lives in its module's namespace —

selfhost/cmd/wcc/cgen.ww

@@ -1730,6 +1730,29 @@ fn deflookuprhs(c: *cgen, name: str) *node = {
 	return nil;
 };
 
+// deflookuprhsmod — same-module-first walk for `mod.NAME` references.
+// Trio-leaf *mod variant mirroring fnretlookupmod (#31) / fnparamslookupmod
+// (#28) / enumlookupmod (#4a). Module-qualified `alpha.MSG` from a third
+// module needs the explicit alpha hint; deflookuprhs prefers c.curmod
+// (which doesn't match either source module on a 3rd-module qualifier)
+// and falls back to head-pick, possibly inlining beta.MSG's strlit when
+// both alpha and beta declare same-leaf str defs. cgdot's mod-qualified
+// str-def value-load routes here so a cross-module N_DOT collision
+// resolves to the explicit module. Falls back to deflookuprhs's bare-
+// leaf two-pass when no module matches.
+fn deflookuprhsmod(c: *cgen, name: str, mod: str) *node = {
+	if (mod.len > 0) {
+		let e: *defent = c.defs;
+		for (e != nil) {
+			if (streq(e.dname, name)) {
+				if (streq(e.dmod, mod)) { return e.drhs; };
+			};
+			e = e.dnext;
+		};
+	};
+	return deflookuprhs(c, name);
+};
+
 // ---- module-private symbol map --------------------------------------
 //
 // Every non-FFI top-level fn decl lives in its module's namespace —

selfhost/cmd/wcc/cgenexpr.ww

@@ -1744,8 +1744,11 @@ fn cgdot(c: *cgen, n: *node) void = {
 			// strlit-inline matches cstage Sdef walk #2 in
 			// cmd/w6c/cgen.c N_DOT mod-qualified. Without this
 			// the MOVQ leaf(SB) fallback emits a bogus ref
-			// (`alpha.MSG(SB)`, never DATAW-defined). Filed #12.
-			let drhs: *node = deflookuprhs(c, fld);
+			// (`alpha.MSG(SB)`, never DATAW-defined). lhs.str is
+			// the explicit module hint — a 3rd-module qualifier
+			// `alpha.MSG` from gamma needs alpha (not c.curmod)
+			// to beat a head-of-c.defs beta.MSG collision (#11).
+			let drhs: *node = deflookuprhsmod(c, fld, lhs.str);
 			if (drhs != nil) {
 				if (drhs.kind == nkind.N_STRLIT) {
 					let bytes: str = drhs.str;

selfhost/cmd/wwdump/main.combined.ww

@@ -12673,8 +12673,11 @@ fn cgdot(c: *cgen, n: *node) void = {
 			// strlit-inline matches cstage Sdef walk #2 in
 			// cmd/w6c/cgen.c N_DOT mod-qualified. Without this
 			// the MOVQ leaf(SB) fallback emits a bogus ref
-			// (`alpha.MSG(SB)`, never DATAW-defined). Filed #12.
-			let drhs: *node = deflookuprhs(c, fld);
+			// (`alpha.MSG(SB)`, never DATAW-defined). lhs.str is
+			// the explicit module hint — a 3rd-module qualifier
+			// `alpha.MSG` from gamma needs alpha (not c.curmod)
+			// to beat a head-of-c.defs beta.MSG collision (#11).
+			let drhs: *node = deflookuprhsmod(c, fld, lhs.str);
 			if (drhs != nil) {
 				if (drhs.kind == nkind.N_STRLIT) {
 					let bytes: str = drhs.str;
@@ -20880,6 +20883,29 @@ fn deflookuprhs(c: *cgen, name: str) *node = {
 	return nil;
 };
 
+// deflookuprhsmod — same-module-first walk for `mod.NAME` references.
+// Trio-leaf *mod variant mirroring fnretlookupmod (#31) / fnparamslookupmod
+// (#28) / enumlookupmod (#4a). Module-qualified `alpha.MSG` from a third
+// module needs the explicit alpha hint; deflookuprhs prefers c.curmod
+// (which doesn't match either source module on a 3rd-module qualifier)
+// and falls back to head-pick, possibly inlining beta.MSG's strlit when
+// both alpha and beta declare same-leaf str defs. cgdot's mod-qualified
+// str-def value-load routes here so a cross-module N_DOT collision
+// resolves to the explicit module. Falls back to deflookuprhs's bare-
+// leaf two-pass when no module matches.
+fn deflookuprhsmod(c: *cgen, name: str, mod: str) *node = {
+	if (mod.len > 0) {
+		let e: *defent = c.defs;
+		for (e != nil) {
+			if (streq(e.dname, name)) {
+				if (streq(e.dmod, mod)) { return e.drhs; };
+			};
+			e = e.dnext;
+		};
+	};
+	return deflookuprhs(c, name);
+};
+
 // ---- module-private symbol map --------------------------------------
 //
 // Every non-FFI top-level fn decl lives in its module's namespace —

test/wcc/747_def_modqual_modshadow.c

@@ -0,0 +1,221 @@
+/*
+ * 747_def_modqual_modshadow — sentinel for task #11: cstage Sdef walk #2
+ * (cmd/w6c/cgen.c N_DOT mod-qualified bare-value load) + wwstage
+ * deflookuprhsmod (selfhost/cmd/wcc/cgenexpr.ww cgdot N_DOT branch).
+ * Pins `alpha.MSG` from a third module gamma to resolve via n->lhs->str
+ * (= "alpha") rather than head-pick of c.defs / sdefs so the inlined
+ * strlit address + length come from alpha's MSG even when beta declares
+ * a same-leaf MSG sitting at the head of the table.
+ *
+ * Pre-fix cstage walk #2 had no prefer-pass at all — head-pick of sdefs
+ * regardless of the explicit qualifier. Pre-fix wwstage called the bare-
+ * leaf deflookuprhs (#4c) which prefers c.curmod and falls back to head
+ * on mismatch — for a 3rd-module qualifier `alpha.MSG` from gamma the
+ * curmod hint matches nothing and the head-pick lands on beta.MSG.
+ * Sister of #4c's deflookuprhs / Sdef walk #3 graduation: the *mod
+ * variant pattern that #4a (enumlookupmod), #28 (fnparamslookupmod) and
+ * #31 (fnretlookupmod) established for N_DOT qualifier disambiguation
+ * — the dotted LHS module name is the right hint source, not c.curmod.
+ *
+ * Cstage walk #2 grows the sdef_mod_match_hint helper (sister of the
+ * existing sdef_mod_match which keys c->cur_mod) and routes the walk
+ * through it with n->lhs->str. Wwstage grows deflookuprhsmod(c, name,
+ * mod) (sister of deflookuprhs) and cgdot routes the mod-qualified
+ * branch through it with lhs.str. Both stages converge on the same
+ * polarity → byte-id holds on the 3rd-module qualifier shape.
+ *
+ * Was blocked solely on #12 (wwstage str-def value-load shape); #12
+ * landed in d985622 so the sentinel-flip byte-id check now passes.
+ *
+ * Pin: row 1 sentinel-flips both stages' new prefer-pass — revert and
+ * row 1 fails on both (LEAQ of beta.MSG's strlit label instead of
+ * alpha.MSG's, and MOVQ $27 instead of $38). Asserts the matching
+ * `MOVQ $38,` immediate inside gamma.gfn TEXT + bad_imm `MOVQ $27,`
+ * anti-check on each stage plus cs-vs-ws byte-id per row.
+ */
+#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 immediate that MUST appear */
+	const char *bad_imm;	/* the immediate that MUST NOT appear */
+};
+
+/* Source orderings: alpha declared before beta so beta.MSG sits at the
+ * HEAD of c.defs / sdefs after the prepend-walk of collectdefs /
+ * sdef_collect. Caller lives in a third module gamma (not alpha, not
+ * beta) so c.curmod / c->cur_mod doesn't accidentally match either
+ * source module — only the lhs.str / n->lhs->str hint resolves to
+ * alpha. Strlit lengths 39 vs 27 chosen so neither digit-string is a
+ * substring of the other and neither aliases a common frame/offset
+ * immediate the asm emits (0/8/16/24/32/40/48 etc).
+ *
+ * The TY_FN branch above walk #2 in cstage already uses n->lhs->str via
+ * mafn — this row pins the parallel polarity on the Sdef walk just
+ * below it. */
+static const struct row rows[] = {
+	{ "third_module_qualifier_shadow",
+	  "package gamma;\n"
+	  "import alpha;\n"
+	  "import beta;\n"
+	  "export fn main() i32 = { return 0; };\n"
+	  "export fn gfn() str = { return alpha.MSG; };\n"
+	  "package alpha;\n"
+	  "export def MSG: str = \"alpha_modqual_pin_38chr_aaaaaaaaaaaaaa\";\n"
+	  "package beta;\n"
+	  "export def MSG: str = \"beta_modqual_pin_27chr_BBBB\";\n",
+	  "TEXT gamma.gfn", "$38,", "$27," },
+};
+
+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/dmq_%d_%d.ww", getpid(), i);
+	snprintf(out_s, cap, "/tmp/dmq_%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, want_imm MUST appear
+ * and bad_imm MUST NOT. bad_imm flags pre-fix head-walk picking
+ * beta.MSG's strlit length (27) instead of alpha.MSG's (39). */
+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 MSG\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,
+			    "def_modqual_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,
+			    "def_modqual_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,
+			    "def_modqual_modshadow[%s]: cstage vs wwstage asm differs\n",
+			    rows[i].label);
+			fail++;
+		}
+
+		unlink(cs_path); unlink(ws_path);
+	}
+
+	if (fail) {
+		fprintf(stderr,
+		    "def_modqual_modshadow: %d/%d fixtures failed\n", fail, total);
+		return 1;
+	}
+	printf("def_modqual_modshadow: %d/%d ok\n", total, total);
+	return 0;
+}