GCC C语言处理主要函数之c_common_init

c_common_init:
 
Front end initialization common to C, ObjC and C++.  */
bool c_common_init (void)
{
  /* Set up preprocessor arithmetic.  Must be done after call to
     c_common_nodes_and_builtins for type nodes to be good.  */
  cpp_opts->precision = TYPE_PRECISION (intmax_type_node);
  cpp_opts->char_precision = TYPE_PRECISION (char_type_node);
  cpp_opts->int_precision = TYPE_PRECISION (integer_type_node);
  cpp_opts->wchar_precision = TYPE_PRECISION (wchar_type_node);
  cpp_opts->unsigned_wchar = TYPE_UNSIGNED (wchar_type_node);
  cpp_opts->bytes_big_endian = BYTES_BIG_ENDIAN;
  /* This can't happen until after wchar_precision and bytes_big_endian
     are known.  */
  cpp_init_iconv (parse_in);
  if (version_flag)
    {
      int i;
      fputs ("Compiler executable checksum: ", stderr);
      for (i = 0; i