diff --git a/boot.c b/boot.c
index ba8b11e..9093ce6 100644
--- a/boot.c
+++ b/boot.c
@@ -249,12 +249,16 @@ void next_token() {
     } else if (ch == '/') {
         int ch2 = getchar();
         if (ch2 == '/') {
-            while ((ch = getchar()) != '\n');
+            do ch = getchar(); while (ch != '\n' && ch != -1);
             next_token();
             return;
         } else if (ch2 == '*') {
             while (1) {
                 ch = getchar();
+                if (ch == -1) {
+                    eprintf("expecting '*/'\n");
+                    exit(1);
+                }
                 if (ch == '*') {
                     ch = getchar();
                     if (ch == '/') {
@@ -773,7 +777,7 @@ int parse_postfix_expr() {
             store_t0(reg);
             printf("  addi t0, t0, %d\n", step_of(type));
             store_t0(lhs);
-            return reg;
+            lhs = reg;
         } else if (token_type == TOKEN_DEC) {
             int type = local_type[lhs];
             int reg = next_reg(type);
@@ -781,11 +785,11 @@ int parse_postfix_expr() {
             store_t0(reg);
             printf("  addi t0, t0, -%d\n", step_of(type));
             store_t0(lhs);
-            return reg;
+            lhs = reg;
         } else if (token_type == TOKEN_BRACKET_LEFT) {
             int rhs = parse_expr();
             expect_token(TOKEN_BRACKET_RIGHT);
-            return indirection_of(asm_add(lhs, rhs));
+            lhs = indirection_of(asm_add(lhs, rhs));
         } else if (token_type == TOKEN_PAREN_LEFT) {
             int arg = 0;
             int args[8];
@@ -817,12 +821,13 @@ int parse_postfix_expr() {
             load_address(0, lhs);
             printf("  jalr t0\n");
             printf("  mv t0, a0\n");
-            return materialize_t0(local_type[lhs]);
+            lhs = materialize_t0(local_type[lhs]);
         } else {
             unget_token();
-            return lhs;
+            break;
         }
     }
+    return lhs;
 }
 
 int parse_prefix_expr() {
diff --git a/demo/queen.c b/demo/queen.c
new file mode 100644
index 0000000..ac4a310
--- /dev/null
+++ b/demo/queen.c
@@ -0,0 +1,47 @@
+int printf(const char format[], ...);
+int putchar(int ch);
+
+int a[9];
+
+void output() {
+    for (int i = 1; i <= 8; ++i) {
+        for (int j = 1; j <= 8; ++j) {
+            if (a[i] == j) {
+                putchar('x');
+            } else {
+                putchar('-');
+            }
+        }
+        putchar('\n');
+    }
+    putchar('\n');
+}
+
+int ok(int x, int y) {
+    for (int i = 1; i <= x - 1; ++i) {
+        if (a[i] == y || a[i] - i == y - x || a[i] + i == y + x) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+void queen(int x) {
+    if (x > 8) {
+        output();
+        a[0]++;
+    }
+    for (int y = 1; y <= 8; ++y) {
+        if (ok(x, y)) {
+            a[x] = y;
+            queen(x + 1);
+            a[x] = 0;
+        }
+    }
+}
+
+int main() {
+    queen(1);
+    printf("solutions: %d\n", a[0]);
+    return 0;
+}
\ No newline at end of file