In devkitPPC release 29, now the compiler gives a warning for "ftruncate" (undefined function).
Indeed the include file (unist.h) changed in respect to r28.
However the compiler can link the function.
#if defined(__CYGWIN__) || defined(__rtems__) || defined(__aarch64__) || defined (__arm__) || defined(__sh__) || defined(__SPU__)
int _EXFUN(ftruncate, (int __fd, off_t __length));
int _EXFUN(truncate, (const char *, off_t __length));
PPC architecture seems not included in the OR list.