ref: 46d3eab0b1e077005fcc4a7bc5257be9a411d1a1 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); }