ref: 81b6d6367c1c9c957ca910e5f8b5fb70adfa9c21 dir: /lib/c/src/isalnum.c/
#define __USE_MACROS #include <ctype.h> #undef isalnum int isalnum(int c) { return (__ctype+1)[c] & (_U|_L|_D); }