Re: curses_trace() - version 6.6

Thank you for the response.

For me the man page sounded like "curses_trace()" is always available no
matter how you compile the library.

I thought calling the function twice to check for the return code is a
little awkward.
But if that is the official way to do it - I'm fine with it. :)

On Wed, Aug 5, 2026 at 9:09 PM Thomas Dickey <[email protected]>
wrote:

> On Wed, Aug 05, 2026 at 07:41:24PM +0200, Björn Försterling wrote:
> > 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.
>
> The man page does say that:
>
> DESCRIPTION
>        The curses trace routines are used for debugging the ncurses
> libraries,
>        as well as applications which use the ncurses libraries.  Some
> limita‐
>        tions apply:
>
>        •   Aside from curses_trace, the other functions are normally
> available
>            only with the debugging library e.g., libncurses_g.a.
>
>            All  of the trace functions may be compiled into any model
> (shared,
>            static, profile) by defining the symbol TRACE.
>
>        •   Additionally, the functions which use cchar_t  are  only
> available
>            with the wide-character configuration of the libraries.
>
> ...and "normally available" should tell you that it's probably not
> available
> for your configuration unless you did something such as recompile.
>
> I did this to allow developers to substitute a debugging version, e.g.,
> using
> LD_LIBRARY_PATH (which works well enough except for MacOS...).  If the
> entrypoint were only available when it's fully functional, that wouldn't
> be useful for this case.
>
> Your application can check the return value to see if it was available:
>
>        The curses_trace function is always available, whether or not the
> other
>        trace functions are available:
>
>        •   If  tracing is available, calling curses_trace with a nonzero
> para‐
>            meter updates the trace mask, and returns the previous trace
> mask.
>
>            When the trace mask is nonzero, ncurses creates the file
> “trace” in
>            the current directory for output.  If the file already
> exists,  no
>            tracing is done.
>
>        •   If tracing is not available, curses_trace returns zero (0).
>
> > 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.
>
> yes :-)
>
> > But how do you check if tracing is available?
>
> call the function twice:
>
>         curses_trace(TRACE_MAXIMUM);
>         rc = trace(TRACE_NORMAL);
>
> curs_set and umask do something like that with return-codes.
>
> --
> Thomas E. Dickey <[email protected]>
> https://invisible-island.net
>