打开已存在的文件时出现分段错误

Question

我正在尝试打开一个已经存在的文件：

    program writeeven
    implicit none
    logical :: alive
    inquire(file='even.txt', exist=alive)
   if (alive) then
      print *, 'file is existed'
      open(12, file='even.txt')
   else
      print *, 'file is not existed'
   end if

   end program writeeven

程序给出以下消息：

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

如何打开现有文件并阅读消息？