gcc/testsuite/gcc.dg/cpp/undef2.c

   1 /* C99 6.10.8 para 4: None of [the predefined macro names] shall be
   2    the subject of a #define or an #undef preprocessing directive.  We
   3    pass -fno-show-column as otherwise dejagnu gets confused.  */
   4
   5 /* { dg-do preprocess } */
   6 /* { dg-options "-fno-show-column" } */
   7
   8 #undef __DATE__         /* { dg-warning "undefining" "__DATE__" } */
   9 #undef __TIME__         /* { dg-warning "undefining" "__TIME__" } */
  10 #undef __FILE__         /* { dg-warning "undefining" "__FILE__" } */
  11 #undef __LINE__         /* { dg-warning "undefining" "__LINE__" } */
  12 #undef __STDC__         /* { dg-warning "undefining" "__STDC__" } */
  13
  14 /* These should be protected from #undef, but aren't, because they
  15    are set with normal #define commands - and on top of that, some
  16    of them are library properties, outside our control.  To consider:
  17    warn about undefining/redefining any identifier beginning with
  18    __STDC_ .
  19
  20    __STDC_HOSTED__
  21    __STDC_VERSION__
  22    __STDC_IEC_559__
  23    __STDC_IEC_559_COMPLEX__
  24    __STDC_ISO_10646__
  25  */