curses_trace() - version 6.6

Hello,

the man page "curs_trace" says:
> The curses_trace function is always available [...]

But you have to configure ncurses with "--with-trace" so that
`curses_trace()` actually outputs to a "trace" file, which is not clear
from the man page.

And `curses_trace(TRACE_MAXIMUM)` seems to return 0 even when tracing is
available and writing to a file called "trace" works.
Probably because the previous bitmask was 0.
But how do you check if tracing is available?

Regards
Björn