#include <features.h>
#if defined(__GNUC__) && defined(__GLIBC_PREREQ)
# if __GLIBC_PREREQ(2,3)
    /* squash __ctype_to{upper,lower}_loc and avoid including the header */
#   define _CTYPE_H 1
    extern int isalnum(int c);
    extern int isalpha(int c);
    extern int isascii(int c);
    extern int isblank(int c);
    extern int iscntrl(int c);
    extern int isdigit(int c);
    extern int isgraph(int c);
    extern int islower(int c);
    extern int isprint(int c);
    extern int ispunct(int c);
    extern int isspace(int c);
    extern int isupper(int c);
    extern int isxdigit(int c);
    /* squash realpath@GLIBC_2.3 */
#   include <stdlib.h>
    asm (".symver realpath, realpath@GLIBC_2.0");
# endif
#endif
