problem with mpf_get_str?

[Paul Zimmermann]

       Hi,

the documentation of mpf_get_str says:

     If STR is `NULL', the result string is allocated using the current
     allocation function (*note Custom Allocation::).  The block will be
     `strlen(str)+1' bytes, that being exactly enough for the string and
     null-terminator.

However it is not said how to ***free*** that string, in particular if the
default free function was modified (either with mp_set_memory_functions,
or from some other application).

Paul