At Fri, 14 Jul 2006 15:36:07 +0200,
Helmut Eller wrote:
My suspicion is that SBCL's printer is not thread-safe. In particular, the use of sb-impl::*previous-case* looks like it could lead the kind of bugs that you see.
Yup SBCL bug, there is a bunch of special variables internal to code/print.lisp, which are never bound when threads are started and as such are shared between all threads.. Ie *internal-symbol-output-fun* is global and is clobbered by every thread when *print-case* is changed, so it always uses the value that was set by the last thread which changed *print-case* to a different value.
Now that I've figured this out, I remember giving up playing with kpax and portable-aserve, because of too many bugs where the case was bad (it uses the :keyword for HTTP headers, and wrong case was popping up all over the place). Now I think there is nothing wrong with portable-aserve and kpax, but instead I was hitting the same bug.
--- SBCL test that (may only be failing on SMP hardware) --- CL-USER> (let ((iterations 100000)) (sb-thread:make-thread (lambda () (let ((*print-case* :downcase)) (dotimes (i iterations) (assert (string= (with-output-to-string (s) (prin1 'FOO s)) "foo")))w))) (sb-thread:make-thread (lambda () (let ((*print-case* :upcase)) (dotimes (i iterations) (assert (string= (with-output-to-string (s) (prin1 'FOO s)) "FOO")))))) ) --- end ---
Regards, Max