ref: 5fffd4ac0ac75d6ba1d8e978a9c618ede9e5f2e5 dir: /lib/c/isalnum.c/
#define __USE_MACROS #include <ctype.h> #undef isalnum int isalnum(int c) { return (__ctype+1)[c] & (_U|_L|_D); }