HelenOS sources

fputwc            771 uspace/lib/c/generic/io/io.c 	return fputwc(wc, stdout);
fputwc            124 uspace/lib/c/include/stdio.h extern wint_t fputwc(wchar_t, FILE *);
fputwc            124 uspace/lib/posix/include/libc/stdio.h extern wint_t fputwc(wchar_t, FILE *);
HelenOS homepage, sources at GitHub