setlocale() is implemented in the C
library Internationalization package.
Functions fileno() and
fdopen() are implemented in the C
library STDIO package.
Functions getc_unlocked(),
getchar_unlocked(),
putc_unlocked() and
putchar_unlocked() are defined
but are currently identical to their non-unlocked
equivalents.
strtok_r(), asctime_r(),
ctime_r(), gmtime_r(),
localtime_r() and
rand_r() are all currently in
the C library, alongside their non-reentrant versions.