ref: 7bf8c43ed5c66b80bb4c9b1ac1c6fdcfe72b9f19 dir: /lib/c/isalnum.c/
#define __USE_MACROS #include <ctype.h> #undef isalnum int isalnum(int c) { return (__ctype+1)[c] & (_U|_L|_D); }