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. */ 3 4/* { dg-do preprocess } */ 5 6#undef __DATE__ /* { dg-warning "undefining" "__DATE__" } */ 7#undef __TIME__ /* { dg-warning "undefining" "__TIME__" } */ 8#undef __FILE__ /* { dg-warning "undefining" "__FILE__" } */ 9#undef __LINE__ /* { dg-warning "undefining" "__LINE__" } */ 10#undef __STDC__ /* { dg-warning "undefining" "__STDC__" } */ 11 12/* These should be protected from #undef, but aren't, because they 13 are set with normal #define commands - and on top of that, some 14 of them are library properties, outside our control. To consider: 15 warn about undefining/redefining any identifier beginning with 16 __STDC_ . 17 18 __STDC_HOSTED__ 19 __STDC_VERSION__ 20 __STDC_IEC_559__ 21 __STDC_IEC_559_COMPLEX__ 22 __STDC_ISO_10646__ 23 */ 24