GCC主要数据结构之c_lang

/* C language kind, used when calling cpp_create_reader.  */
enum c_lang {CLK_GNUC89 = 0, CLK_GNUC99, CLK_GNUC11,
      CLK_STDC89, CLK_STDC94, CLK_STDC99, CLK_STDC11,
      CLK_GNUCXX, CLK_CXX98, CLK_GNUCXX11, CLK_CXX11,
      CLK_GNUCXX14, CLK_CXX14, CLK_GNUCXX1Z, CLK_CXX1Z, CLK_ASM};