teepeedee2

確かに速い。

diff --git a/src/lib/utils.lisp b/src/lib/utils.lisp
index 2ce21f0..e200cb8 100644
--- a/src/lib/utils.lisp
+++ b/src/lib/utils.lisp
@@ -57,8 +57,9 @@
 (defun report-error (err &key (stream *error-output*))
   (format stream "~&ERROR ~A, ~A:~%~A~&"
          (ignore-errors (princ-to-string err))
-         (with-output-to-string (*standard-output*) (describe err))
-         (trivial-backtrace:backtrace-string)))
+         (with-output-to-string (*standard-output*) (describe err))
+          (with-output-to-string (out)
+            (trivial-backtrace:print-backtrace-to-stream out))))

 (defun backtrace-description (err)
   (report-error err :stream nil))