Fix segfault

Author: tyfkda

src/cc/frontend/parser.c

@@ -676,6 +676,8 @@ static Stmt *parse_stmt(void) {
 
   // expression statement.
   Expr *val = parse_expr();
+  if (val == NULL)
+    val = new_expr_fixlit(&tyInt, tok, 0);  // Dummy
   consume(TK_SEMICOL, "`;' expected");
   return new_stmt_expr(str_to_char_array_var(curscope, val));
 }

src/cc/frontend/parser_expr.c

@@ -825,6 +825,8 @@ Expr *parse_assign(void) {
 Expr *parse_const_fixnum(void) {
   parsing_stmt = false;
   Expr *expr = parse_precedence(PREC_LOGIOR);
+  if (expr == NULL)
+    return NULL;  // Error is already reported.
   if (is_const(expr) && is_fixnum(expr->type->kind))
     return expr;
   parse_error(PE_NOFATAL, expr->token, "constant integer expected");