ref: 1b93241842ebf1e5a7efaf62b1fcaf02a7c6d4e5 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); }