[Bug preprocessor/81515] New: C pre-processor allows invalid words

["barto at cambridgesemantics dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81515

            Bug ID: 81515
           Summary: C pre-processor allows invalid words
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: barto at cambridgesemantics dot com
  Target Milestone: ---

The following will parse successfully
#if BADTEST
#include <stdio.h>
#ele
#include <ctype.h>
#endif

#include <stdlib.h>

int main(int, char **)
{
  exit(0);
}