clang -O2  -Wall -Wextra -Werror=implicit-function-declaration uchar/c16rtomb.c -o uchar/c16rtomb -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm  -lintl
uchar/c16rtomb.c:4:10: fatal error: 'uchar.h' file not found
#include <uchar.h>
         ^
1 error generated.