ref: 7d9ec5573f3348f6d9c26c5eb6945f880d1488f5 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); }