[CM] Examples of printing out errors in S7?

Iain Duncan iainduncanlists at gmail.com
Fri Apr 10 10:37:28 PDT 2020

Thanks Bill, I'll chew on all that and see how far I can get. Much


On Fri, Apr 10, 2020 at 10:15 AM <bil at ccrma.stanford.edu> wrote:

> Normally, s7_error (called either from C or scheme) sends its error
> message
> to the current error-port.  It defaults to *stderr*, so in GUI-based
> apps,
> you may need to redirect the output to your interface.  One example is
> s7/tools/grepl.c.  Its evaluator function wraps up the s7_eval_c_string:
>    old_port = s7_set_current_error_port(s7, s7_open_output_string(s7));
>    ...
>    result = s7_eval_c_string(s7, text);
>    errmsg = s7_get_output_string(s7, s7_current_error_port(s7));
>    ...
> and if errmsg is not NULL, it posts it somewhere (via
> glistener_append_text,
> since it's using the repl in glistener.c).  Snd uses largely the same
> code (snd-motif.c and glistener.c if in gtk).  See also s7.html under
> "glistener".  If you don't want s7's error messages, you can go down
> a level via *error-hook*.
> I don't know why your program exits silently, but a first fix might be
> to wrap the string being evaluated in a catch (s7.html under "errors").
> If you're calling s7_apply_function, you may need to make sure
> a catch exists.  In Snd, if I remember right, this involves
> top_level_catch (snd.c, snd-nogui.c, etc).  Or you can use s7_call
> instead of s7_apply_function.
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