diff --git a/sbc/Makefile b/sbc/Makefile
index c783d04..39e9a0c 100644
--- a/sbc/Makefile
+++ b/sbc/Makefile
@@ -11,7 +11,7 @@ out: entry.o out.o lib.o
 	nasm -f elf64 $< -o $@
 
 out.nasm: program.sbl
-	deno run --allow-read --allow-write --check main.ts $<
+	deno run --allow-read --allow-write --check main.ts $< $@
 
 clean:
 	rm -rf out.asm out.o lib.o entry.o out
diff --git a/sbc/ast.ts b/sbc/ast.ts
index 6550c55..b144a4e 100644
--- a/sbc/ast.ts
+++ b/sbc/ast.ts
@@ -83,6 +83,7 @@ export type Ty = {
 
 export type TyKind =
     | { tag: "error" }
+    | { tag: "void" }
     | { tag: "ident"; ident: string }
     | { tag: "ptr"; ty: Ty };
 
diff --git a/sbc/front.ts b/sbc/front.ts
index 603827d..656a60f 100644
--- a/sbc/front.ts
+++ b/sbc/front.ts
@@ -188,6 +188,8 @@ export class Checker {
             switch (k.tag) {
                 case "error":
                     return { tag: "error" };
+                case "void":
+                    return { tag: "void" };
                 case "ident": {
                     switch (k.ident) {
                         case "int":
@@ -232,6 +234,8 @@ export class Checker {
 
         if (a.tag === "error" || b.tag === "error") {
             return ok(a);
+        } else if (both("void")) {
+            return ok(a);
         } else if (both("int")) {
             return ok(a);
         } else if (both("str")) {
@@ -912,7 +916,14 @@ export class Parser {
     }
 
     private parseTy(): AstTy {
-        if (this.eat("ident")) {
+        if (this.eat("(")) {
+            if (this.eat(")")) {
+                return this.ty({ tag: "void" }, this.eaten!.line);
+            } else {
+                this.report("expected ')'");
+                return this.ty({ tag: "error" }, this.last!.line);
+            }
+        } else if (this.eat("ident")) {
             return this.ty(
                 { tag: "ident", ident: this.eaten!.identVal! },
                 this.eaten!.line,
diff --git a/sbc/main.ts b/sbc/main.ts
index eb46dc6..7931c0c 100644
--- a/sbc/main.ts
+++ b/sbc/main.ts
@@ -8,7 +8,13 @@ import { AsmGen } from "./asm_gen.ts";
 import { optimizeLir } from "./lir_optimize.ts";
 
 async function main() {
-    const text = await Deno.readTextFile(Deno.args[0]);
+    const inputFile = Deno.args[0];
+    const outputFile = Deno.args[1];
+    if (!inputFile || !outputFile) {
+        throw new Error("incorrect arguments");
+    }
+
+    const text = await Deno.readTextFile(inputFile);
 
     const ast = new Parser(text).parse();
     // console.log("=== AST ===");
@@ -44,7 +50,7 @@ async function main() {
     // console.log("=== ASM ===");
     // console.log(asm);
 
-    await Deno.writeTextFile("out.nasm", asm);
+    await Deno.writeTextFile(outputFile, asm);
 }
 
 main();
diff --git a/sbc/program.sbl b/sbc/program.sbl
index fa55611..d0c0c67 100644
--- a/sbc/program.sbl
+++ b/sbc/program.sbl
@@ -11,6 +11,10 @@ fn factorial(v: int) -> int {
     return v * factorial(v - 1);
 }
 
+fn return_void_ptr(ptr: *()) -> *() {
+    return ptr;
+}
+
 #[c_export("sbc_main")]
 fn main() -> int {
     let i = 0;
diff --git a/sbc/ty.ts b/sbc/ty.ts
index 8d9054b..7ce56c2 100644
--- a/sbc/ty.ts
+++ b/sbc/ty.ts
@@ -3,6 +3,7 @@ import * as ast from "./ast.ts";
 export type Ty =
     | { tag: "error" }
     | { tag: "unknown" }
+    | { tag: "void" }
     | { tag: "int" }
     | { tag: "str" }
     | { tag: "ptr"; ty: Ty }
@@ -14,6 +15,8 @@ export function tyToString(ty: Ty): string {
             return `<error>`;
         case "unknown":
             return `<unknown>`;
+        case "void":
+            return `()`;
         case "int":
             return `int`;
         case "str":