Ikumi Keita <ikumi@ikumi.que.jp> writes:

> Hi Andreas, thanks for your reply.
>
>>>>>> Andreas Schwab <schwab@suse.de> writes:
>> On Jun 05 2018, Ikumi Keita <ikumi@ikumi.que.jp> wrote:
>>> (defun xyz (arg)
>>> "dummy"
>>> ;    (cond ((eq arg nil) ; OK
>>> ;    (cond ((eq arg 'abc) ; OK
>>> ;    (cond ((eq arg 'def) ; OK
>>> (cond ((eq arg 'default) ; NG
>
>> The byte-compiler uses 'default as a magic symbol, which breaks this
>> case.
>
> Does this mean that this behavior is a (new) designed feature of elisp
> and not a bug?
> If so, is it the respoisibility of the authors of the codes to rewrite
> not to use `default' or else to make sure to set
> `byte-compile-cond-use-jump-table' to nil at byte compile?

I for one consider this a bug, for 2 reasons:

1) It's not reasonable to expect a Lisp programmer to just know that
using the symbol default is problematic.

2) It creates diverging behavior between compiled and non-compiled Lisp.

To that end, I've made a small patch to rectify the behavior. Instead of
hardcoding a symbol, it uses gensym to create a unique one. I did a full
build of Emacs, as well as ran 'make check' and had identical results
pre- and post-change, so I'm reasonably sure it's correct.

Comments and corrections are of course welcomed.

HTH,
-- 
~Robert Cochran

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