Function svn_string_createv 

pub unsafe extern "C" fn svn_string_createv(
    pool: *mut apr_pool_t,
    fmt: *const c_char,
    ap: *mut __va_list_tag,
) -> *mut svn_string_t

Create a new string by printf-style formatting using @c fmt and @a ap. This is the same as svn_string_createf() except for the different way of passing the variable arguments.