rt: move slice append helpers from lib/slices/ into libwwrt.a

Makefile

@@ -39,7 +39,8 @@ W6L_SRC	= cmd/w6l/main.c cmd/w6l/obj.c cmd/w6l/sym.c cmd/w6l/pass.c cmd/w6l/out.
 W6L_OBJ	= $(W6L_SRC:cmd/w6l/%.c=$(OBJ)/w6l/%.o)
 
 RT_S	= rt/start.s rt/syscall.s rt/alloc.s rt/streq.s rt/abort.s
-RT_OBJ	= $(RT_S:rt/%.s=$(OBJ)/rt/%.o)
+RT_WW	= rt/append.ww
+RT_OBJ	= $(RT_S:rt/%.s=$(OBJ)/rt/%.o) $(RT_WW:rt/%.ww=$(OBJ)/rt/%.o)
 
 # Cstage: one-time C bootstrap (see BOOTSTRAP.md). Built by `cc`.
 # Goes away at v1.0, replaced by a checked-in stage-0 binary.
@@ -191,6 +192,14 @@ $(BIN)/ww_ww: selfhost/cmd/ww/main.ww selfhost/cmd/wcc/mem.ww lib/os/os.ww \
 $(OBJ)/rt/%.o: rt/%.s $(BIN)/w6a | $(OBJ)/rt
 	$(BIN)/w6a -o $@ $<
 
+# ww-side runtime helpers (rt/*.ww): compile via w6c to .s, then w6a.
+# Each .ww module is standalone — uses @symbol FFI for rt_alloc/rt_free
+# rather than `use os;` so no bundling is required.
+$(OBJ)/rt/%.s: rt/%.ww $(BIN)/w6c | $(OBJ)/rt
+	$(BIN)/w6c $< > $@
+$(OBJ)/rt/%.o: $(OBJ)/rt/%.s $(BIN)/w6a | $(OBJ)/rt
+	$(BIN)/w6a -o $@ $<
+
 $(LIB)/libwwrt.a: $(RT_OBJ) | $(LIB)
 	$(AR) rcs $@ $(RT_OBJ)
 

rt/append.ww

@@ -1,25 +1,25 @@
-// slices — generic slice helpers, written without generics.
+// rt/append.ww — slice runtime helpers, archived into libwwrt.a.
 //
-// CLAUDE.md forbids generics, so we mint per-element-type variants.
-// Hare's `append` builtin is what these stand in for: each takes a
-// *[]T plus an item, grows the storage if needed, and updates the
-// slice header in place. The user passes `&s` because we mutate
-// through the pointer.
+// The compiler lowers `append(s, v)` to a CALL to one of these by
+// element size (1 byte → appendu8, else → appendi64). User code
+// never `use`s this — the symbol comes in via the runtime archive,
+// like rt_alloc and rt_streq.
 
-use os;
+@symbol("rt_alloc") fn alloc(n: u64) *void;
+@symbol("rt_free")  fn free(p: *void, n: u64) void;
 
 export fn appendu8(s: *[]u8, v: u8) void = {
 	if (s.len >= s.cap) {
 		let nc: i32 = s.cap * 2;
 		if (nc < 8) { nc = 8; };
-		let np: *u8 = os.alloc(nc: u64): *u8;
+		let np: *u8 = alloc(nc: u64): *u8;
 		let i: i32 = 0;
 		for (i < s.len) {
 			np[i] = s.ptr[i];
 			i += 1;
 		};
 		if (s.cap > 0) {
-			os.free(s.ptr: *void, s.cap: u64);
+			free(s.ptr: *void, s.cap: u64);
 		};
 		s.ptr = np;
 		s.cap = nc;
@@ -32,14 +32,14 @@ export fn appendi64(s: *[]i64, v: i64) void = {
 	if (s.len >= s.cap) {
 		let nc: i32 = s.cap * 2;
 		if (nc < 8) { nc = 8; };
-		let np: *i64 = os.alloc((nc * 8): u64): *i64;
+		let np: *i64 = alloc((nc * 8): u64): *i64;
 		let i: i32 = 0;
 		for (i < s.len) {
 			np[i] = s.ptr[i];
 			i += 1;
 		};
 		if (s.cap > 0) {
-			os.free(s.ptr: *void, (s.cap * 8): u64);
+			free(s.ptr: *void, (s.cap * 8): u64);
 		};
 		s.ptr = np;
 		s.cap = nc;

test/wcc/700_e2e.c

@@ -244,24 +244,10 @@ static const struct row rows[] = {
 	  "  x *= 2; x <<= 1; x >>= 2;\n"
 	  "  return x;\n"
 	  "};", 96 },
-	/* user-defined slice append via *[]u8: stdlib slices.appendu8.
-	 * Demonstrates allocator + ptr-to-slice fields + scaled index write. */
-	{ "use os;\n"
-	  "use slices;\n"
-	  "fn main() i32 = {\n"
-	  "  let s: []u8;\n"
-	  "  s.ptr = nil; s.len = 0; s.cap = 0;\n"
-	  "  slices.appendu8(&s, 65u8);\n"
-	  "  slices.appendu8(&s, 66u8);\n"
-	  "  slices.appendu8(&s, 67u8);\n"
-	  "  os.write(1, s.ptr, s.len: u64);\n"
-	  "  os.write(1, \"\\n\".ptr, 1u64);\n"
-	  "  return s.len;\n"
-	  "};", 3 },
 	/* Hare-style builtins: append(s, v) and len(s). The compiler
-	 * lowers these to slices.appendu8 / s.len access. */
+	 * lowers append to a CALL into libwwrt.a's appendu8 / appendi64
+	 * by element size — no `use rt;` or `use slices;` required. */
 	{ "use os;\n"
-	  "use slices;\n"
 	  "fn main() i32 = {\n"
 	  "  let s: []u8;\n"
 	  "  s.ptr = nil; s.len = 0; s.cap = 0;\n"
@@ -281,7 +267,6 @@ static const struct row rows[] = {
 	  "};", 12 },
 	/* variadic append + static qualifier (Hare idiom) */
 	{ "use os;\n"
-	  "use slices;\n"
 	  "fn main() i32 = {\n"
 	  "  let s: []u8;\n"
 	  "  s.ptr = nil; s.len = 0; s.cap = 0;\n"
@@ -298,7 +283,6 @@ static const struct row rows[] = {
 	  "};", 25 },
 	/* Hare-style range loop: for (let x .. slice) iterates elements */
 	{ "use os;\n"
-	  "use slices;\n"
 	  "fn main() i32 = {\n"
 	  "  let s: []u8;\n"
 	  "  s.ptr = nil; s.len = 0; s.cap = 0;\n"
@@ -309,7 +293,6 @@ static const struct row rows[] = {
 	  "};", 100 },
 	/* alloc([], n): fresh empty slice with cap n */
 	{ "use os;\n"
-	  "use slices;\n"
 	  "fn main() i32 = {\n"
 	  "  let s: []u8 = alloc([], 16);\n"
 	  "  append(s, 72u8, 105u8);\n"
@@ -317,7 +300,6 @@ static const struct row rows[] = {
 	  "};", 16 },
 	/* variadic spread: append(dst, src...) iterates src */
 	{ "use os;\n"
-	  "use slices;\n"
 	  "fn main() i32 = {\n"
 	  "  let src: []u8;\n"
 	  "  src.ptr = nil; src.len = 0; src.cap = 0;\n"

test/wcc/900_stdlib.c

@@ -28,7 +28,6 @@ static const char *modules[] = {
 	"lib/bufio/bufio.ww",
 	"lib/fmt/fmt.ww",
 	"lib/net/net.ww",
-	"lib/slices/slices.ww",
 	NULL
 };
 

test/wcc/990_selfhost.c

@@ -210,7 +210,6 @@ probe_dump_diff(const char *bin)
 		"lib/types/types.ww",
 		"lib/sort/sort.ww",
 		"lib/path/path.ww",
-		"lib/slices/slices.ww",
 		"lib/net/net.ww",
 		"lib/encoding/utf8/utf8.ww",
 		"lib/encoding/hex/hex.ww",