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