[U]

1. UID_CACHE_SIZE
2. UID_FROM_HEADER
3. UINTMAX_STRSIZE_BOUND
4. UNGET_FILE
5. UNKNCHAR
6. UNKNOWN
7. UP_KEEPSEL
8. UP_ONLY_CURRENT
9. UP_OPTIMIZE
10. UP_RELOAD
11. URL_FLAGS_NONE
12. URL_NOSLASH
13. URL_USE_ANONYMOUS
14. USBDEVICE_SUPER_MAGIC
15. USE_STATVFS
16. UTF8_CHAR_LEN
17. UX
18. UY