Re: [Emacs-diffs] master babe0d4: Rearrange definition of zerop in subr.el

[Basil L. Contovounesios]

Karl Fogel <address@hidden> writes:

> Paul Eggert <address@hidden> wrote on emacs-devel:
>>Naahhh, I simply overlooked them. Sorry about that. I installed the
>>2nd patch into the emacs-26 branch (since it's just documentation
>>wording cleanup) and the 3rd one into master.
>
> Hunh -- I'm not sure why, but that 3rd patch seems to be leading to build
> lossage on 'master'. Quoting below from 'emacs-diffs':

> I won't have time to look at this further for probably the rest of today, so 
> am posting in case anyone sees the problem right away.

I see Glenn has already reverted the problematic commit [78125f3744],
thanks Glenn!  I'm sorry I didn't try to build myself before suggesting
the change.

[78125f3744]: 2018-07-11 08:27:14 -0700
  Unbreak bootstrap
  
https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=78125f37444acd4f1ec4a0a5b0a338d80672f2ec

Something about

  (declare (compiler-macro (lambda (_) `(= 0 ,number))))

requires both cadr and cddr, and it's not the backquote.  My first
thought is that it relates to the compiler-macro and its expansion by
macroexp.el; can anyone confirm this or correct me?

Would adding a comment along the following lines be welcome?

>From 68d2cc3bb635e117603eb41fc892c9c92a625fb9 Mon Sep 17 00:00:00 2001
From: "Basil L. Contovounesios" <address@hidden>
Date: Wed, 11 Jul 2018 20:11:55 +0300
Subject: [PATCH] ; Add commentary on location of zerop

* lisp/subr.el (zerop): Add commentary explaining why moving the
function's location within the file broke bootstrap in
2018-07-10T23:08:58-07:address@hidden [babe0d4508].

[babe0d4508]: 2018-07-10 23:08:58 -0700
  ; Rearrange definition of zerop in subr.el
  https://git.savannah.gnu.org/cgit/emacs.git/\
commit/?id=babe0d4508273c5fe0a3228b3d2b4d3dcb72cd58
---
 lisp/subr.el | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lisp/subr.el b/lisp/subr.el
index c1d90e3fb1..a5108eb655 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -548,6 +548,9 @@ nbutlast
           (if (> n 0) (setcdr (nthcdr (- (1- m) n) list) nil))
           list))))
 
+;; This function appears here instead of under the 'Basic Lisp
+;; functions' heading because during bootstrap its compiler-macro
+;; requires functions defined under the 'List functions' heading.
 (defun zerop (number)
   "Return t if NUMBER is zero."
   ;; Used to be in C, but it's pointless since (= 0 n) is faster anyway because
-- 
2.18.0

Thanks,

-- 
Basil