wcc/ww: alloc of an alias struct literal chases the alias for size and fill

alloc(alias{...}) keyed the size and field-fill off the syntactic
alias name — it under-allocated and emitted zero field stores. Chase
the alias via structlookupchain to the resolved struct (depth-2
chains verified). The scalar else-branch keeps its pre-existing
benign cs!=ww divergence, surfaced here and deferred as task #57
(site note at the arm). Review item #26.

Makefile

@@ -256,6 +256,7 @@ TESTS	= $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
 	  $(BIN)/test_arrlit_tail_zero_run \
 	  $(BIN)/test_defdim_slice_run \
 	  $(BIN)/test_trystr_run \
+	  $(BIN)/test_allocalias_run \
 	  $(BIN)/test_gunsigned_run \
 	  $(BIN)/test_taggedidx_run \
 	  $(BIN)/test_fnptrcollide_run \
@@ -746,6 +747,16 @@ $(BIN)/test_trystr_run: test/wcc/989_trystr_run.c \
 		$(LIB)/libwwrt.a | $(BIN)
 	$(CC) $(CFLAGS) -o $@ $<
 
+# 989_allocalias_run (#26): alloc(T{...}) for an alias T sizes + field-fills
+# from the alias-chased struct layout, not a name-keyed lookup of the literal
+# head. Builds+runs on BOTH driver twins (rule-10).
+$(BIN)/test_allocalias_run: test/wcc/989_allocalias_run.c \
+		$(BIN)/ww $(BIN)/ww_ww \
+		$(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
+		$(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \
+		$(LIB)/libwwrt.a | $(BIN)
+	$(CC) $(CFLAGS) -o $@ $<
+
 # 989_gunsigned_run (F7-c5, #25): a module-global unsigned ident on the
 # divide/shift/relational path must pick the unsigned opcode. Builds+runs on
 # BOTH driver twins (rule-10). CLASS-M — see the test header.

selfhost/cmd/w6c/main.combined.ww

@@ -28927,14 +28927,14 @@ fn cgalloc(c: *cgen, n: *node) void = {
 	let sz: i32 = 8;
 	let si: *structinfo = nil;
 	if (v.kind == nkind.N_STRUCTLIT) {
-		let trefn: *node = v.lhs;
-		let sname: str;
-		sname.ptr = nil; sname.len = 0;
-		if (trefn != nil) {
-			if (trefn.kind == nkind.N_IDENT) { sname = trefn.str; }
-			else { if (trefn.kind == nkind.N_TNAME) { sname = trefn.str; }; };
-		};
-		si = structlookup(c, sname);
+		// #26: chase the alias chain on the literal's type ref so an
+		// alias head (`type pt = point; alloc(pt{...})`) resolves to
+		// the underlying struct's layout — name-keyed structlookup on
+		// the syntactic head missed it (under-alloc $8 + zero field
+		// stores). Mirrors cstage cgen.c:8223-8240 (type_default chases
+		// named before sizing/walking fields); same alias-chase helper
+		// the #22 sites use.
+		si = structlookupchain(c, v.lhs);
 		if (si != nil) { sz = si.totsize; };
 	};
 	let okl: str = mklabel(c, "alloc_ok");
@@ -29010,6 +29010,10 @@ fn cgalloc(c: *cgen, n: *node) void = {
 			};
 		};
 	} else {
+		// #57 (retained cs!=ww, deferred): scalar/ptr alloc keeps the
+		// default-8 size + MOVQ store; cstage sizes the scalar exactly
+		// ($1/MOVB for u8) and the latent alloc(str|slice) wants 24B not 8.
+		// Byte-id-visible, runtime-benign; not folded into the #26 arm.
 		cgexpr(c, v);
 		emitline("\tMOVQ\t(SP), BX\n");
 		let sop: str = "MOVQ";

selfhost/cmd/wcc/cgenexpr.ww

@@ -5707,14 +5707,14 @@ fn cgalloc(c: *cgen, n: *node) void = {
 	let sz: i32 = 8;
 	let si: *structinfo = nil;
 	if (v.kind == nkind.N_STRUCTLIT) {
-		let trefn: *node = v.lhs;
-		let sname: str;
-		sname.ptr = nil; sname.len = 0;
-		if (trefn != nil) {
-			if (trefn.kind == nkind.N_IDENT) { sname = trefn.str; }
-			else { if (trefn.kind == nkind.N_TNAME) { sname = trefn.str; }; };
-		};
-		si = structlookup(c, sname);
+		// #26: chase the alias chain on the literal's type ref so an
+		// alias head (`type pt = point; alloc(pt{...})`) resolves to
+		// the underlying struct's layout — name-keyed structlookup on
+		// the syntactic head missed it (under-alloc $8 + zero field
+		// stores). Mirrors cstage cgen.c:8223-8240 (type_default chases
+		// named before sizing/walking fields); same alias-chase helper
+		// the #22 sites use.
+		si = structlookupchain(c, v.lhs);
 		if (si != nil) { sz = si.totsize; };
 	};
 	let okl: str = mklabel(c, "alloc_ok");
@@ -5790,6 +5790,10 @@ fn cgalloc(c: *cgen, n: *node) void = {
 			};
 		};
 	} else {
+		// #57 (retained cs!=ww, deferred): scalar/ptr alloc keeps the
+		// default-8 size + MOVQ store; cstage sizes the scalar exactly
+		// ($1/MOVB for u8) and the latent alloc(str|slice) wants 24B not 8.
+		// Byte-id-visible, runtime-benign; not folded into the #26 arm.
 		cgexpr(c, v);
 		emitline("\tMOVQ\t(SP), BX\n");
 		let sop: str = "MOVQ";

selfhost/cmd/wwdump/main.combined.ww

@@ -28927,14 +28927,14 @@ fn cgalloc(c: *cgen, n: *node) void = {
 	let sz: i32 = 8;
 	let si: *structinfo = nil;
 	if (v.kind == nkind.N_STRUCTLIT) {
-		let trefn: *node = v.lhs;
-		let sname: str;
-		sname.ptr = nil; sname.len = 0;
-		if (trefn != nil) {
-			if (trefn.kind == nkind.N_IDENT) { sname = trefn.str; }
-			else { if (trefn.kind == nkind.N_TNAME) { sname = trefn.str; }; };
-		};
-		si = structlookup(c, sname);
+		// #26: chase the alias chain on the literal's type ref so an
+		// alias head (`type pt = point; alloc(pt{...})`) resolves to
+		// the underlying struct's layout — name-keyed structlookup on
+		// the syntactic head missed it (under-alloc $8 + zero field
+		// stores). Mirrors cstage cgen.c:8223-8240 (type_default chases
+		// named before sizing/walking fields); same alias-chase helper
+		// the #22 sites use.
+		si = structlookupchain(c, v.lhs);
 		if (si != nil) { sz = si.totsize; };
 	};
 	let okl: str = mklabel(c, "alloc_ok");
@@ -29010,6 +29010,10 @@ fn cgalloc(c: *cgen, n: *node) void = {
 			};
 		};
 	} else {
+		// #57 (retained cs!=ww, deferred): scalar/ptr alloc keeps the
+		// default-8 size + MOVQ store; cstage sizes the scalar exactly
+		// ($1/MOVB for u8) and the latent alloc(str|slice) wants 24B not 8.
+		// Byte-id-visible, runtime-benign; not folded into the #26 arm.
 		cgexpr(c, v);
 		emitline("\tMOVQ\t(SP), BX\n");
 		let sop: str = "MOVQ";

test/wcc/989_allocalias_run.c

@@ -0,0 +1,155 @@
+/*
+ * 989_allocalias_run (#26) — `alloc(T{...})` where T is an alias of a struct
+ * must size + field-fill from the resolved (alias-chased) struct layout.
+ *
+ * THE BUG (wwstage only): cgalloc looked up the struct layout by the literal
+ * head NAME via structlookup, which scans c.structs by name and never matches
+ * an alias. For `type pt = point; alloc(pt{x=1,y=2})` it found nil, kept the
+ * default size 8 (under-alloc for the 16B struct) and skipped the whole
+ * field-store loop — the *pt pointed at uninitialised heap (rc=0, p.x wrong).
+ * cstage sizes from type_default(v->type) and walks u->fields. THE FIX: chase
+ * the alias chain with structlookupchain on the literal's type ref.
+ *
+ *   row          | shape                              | exit (cs==ww)
+ *   -------------+------------------------------------+--------------
+ *   alias        | type pt=point; alloc(pt{x=1,y=2})  | 0  (was ww 1)
+ *   direct ctrl  | alloc(point{x=1,y=2})              | 0
+ * alias returns p.x*0+ok: pre-fix ww exited 1 (p.x != 1, zero-filled heap).
+ */
+#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; };
+
+static const struct row rows[] = {
+	{ "alias",
+	  "package main;\n"
+	  "import rt;\n"
+	  "type point = struct { x: i64, y: i64 };\n"
+	  "type pt = point;\n"
+	  "export fn main() i32 = {\n"
+	  "	let p: *pt = alloc(pt{x=1,y=2})!;\n"
+	  "	if (p.x != 1) { return 1; };\n"
+	  "	if (p.y != 2) { return 2; };\n"
+	  "	return 0;\n"
+	  "};\n",
+	  0 },
+
+	{ "direct",
+	  "package main;\n"
+	  "import rt;\n"
+	  "type point = struct { x: i64, y: i64 };\n"
+	  "export fn main() i32 = {\n"
+	  "	let p: *point = alloc(point{x=1,y=2})!;\n"
+	  "	if (p.x != 1) { return 1; };\n"
+	  "	if (p.y != 2) { return 2; };\n"
+	  "	return 0;\n"
+	  "};\n",
+	  0 },
+};
+
+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/alal_%d_%d.ww", getpid(), i);
+	snprintf(tmpdir, sizeof tmpdir, "/tmp/alal_%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, "allocalias[cstage][%s]: build/run failed "
+			    "(got %d)\n", rows[i].label, gc);
+			fail++;
+			continue;
+		}
+		if (gc != rows[i].want_exit) {
+			fprintf(stderr, "allocalias[cstage][%s]: exit=%d want=%d\n",
+			    rows[i].label, gc, rows[i].want_exit);
+			fail++;
+		}
+		if (!have_ww) {
+			fprintf(stderr, "allocalias: skip wwstage (no %s)\n", wdrv);
+			continue;
+		}
+		int gw = run_build(wdrv, &rows[i], i);
+		if (gw != gc) {
+			fprintf(stderr, "allocalias[%s]: cs=%d != ww=%d "
+			    "(alloc(alias{}) under-alloc / zero fields — #26)\n",
+			    rows[i].label, gc, gw);
+			fail++;
+		}
+		if (gw != rows[i].want_exit) {
+			fprintf(stderr, "allocalias[wwstage][%s]: exit=%d want=%d\n",
+			    rows[i].label, gw, rows[i].want_exit);
+			fail++;
+		}
+	}
+
+	if (fail) {
+		fprintf(stderr, "allocalias_run: %d/%d checks failed\n",
+		    fail, total);
+		return 1;
+	}
+	printf("allocalias_run: %d/%d ok\n", total, total);
+	return 0;
+}