ref: b7c1a1272d3b24c5fdc3246ed10c0dc9c6f8bd31 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); }