fix double label names

lib/elf/object_writer.rb

@@ -49,6 +49,7 @@ module Elf
       add_symbol "_start", 0
     end
     def add_symbol(name, offset, linkage = Elf::Constants::STB_GLOBAL)
+      return add_symbol( name + "_" , offset ) if @symbol_table.has_name(name)
       @symbol_table.add_func_symbol name, offset, @text, linkage
     end
 

lib/elf/symbol_table_section.rb

@@ -18,6 +18,10 @@ module Elf
       end
     end
 
+    def has_name(name)
+      @strtab.index_for(name)
+    end
+    
     def index_for_name(name)
       @symbols.each_with_index { |sym, idx|
         if (sym[0] == name)