listener: fix hang when stringifying output.

The issue is that when *listener-pprint-p* is set, then
the evaluation is printed using pprinl. The user may have
arranged for that to safely work when there are circular
objects in the print. But then the listener ignores
*listener-pprint-p* when saving the output object as a string
(which is done for the sake of the Ctrl-X Ctrl-P
paste-previous-output feature). The tostring function is used
which can blow up on an object containing circular structure,
even though the object was successfully printed.
The user is puzzled: why was the result of the evaluation
printed completely and perfectly, yet the image has hanged?

* parser.c (repl): Do not use tostring for converting the
evaluated output to a string. Choose between tostring and
tostringp based on the *listener-pprint-p* variable.

1 files changed, 2 insertions, 1 deletions

diff --git a/parser.c b/parser.c
index 0f5d5c99..99c6d728 100644
--- a/parser.c
+++ b/parser.c
@@ -1328,10 +1328,11 @@ val repl(val bindings, val in_stream, val out_stream)
                                            in_stream, out_stream));
         val pprin = cdr(pprint_var);
         val (*pfun)(val, val) = if3(pprin, pprinl, prinl);
+        val (*tsfun)(val) = if3(pprin, tostringp, tostring);
         reg_varl(var_sym, value);
         sethash(result_hash, var_counter, value);
         pfun(value, out_stream);
-        lino_set_result(ls, chk_strdup(c_str(tostring(value))));
+        lino_set_result(ls, chk_strdup(c_str(tsfun(value))));
         lino_hist_add(ls, line_w);
         if (cdr(greedy_eval)) {
           val error_p = nil;