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bug#7070: `load-time-value' local-vars this-kind and that-one
From: |
MON KEY |
Subject: |
bug#7070: `load-time-value' local-vars this-kind and that-one |
Date: |
Sat, 18 Sep 2010 21:43:55 -0400 |
current through BZR-101480 lisp/cl-macs.el macro `load-time-value' has this
branch which if unsatisfied is supposed to fset `byte-compile-file-form':
(and (fboundp 'byte-compile-file-form-defmumble)
(boundp 'this-kind) (boundp 'that-one))
However, luckily the above doesn't happen.
The only locations that bind the variables like this are in
byte-compile-file-form-defmumble' e.g. the local letbound vars
bytecomp-this-kind' and `bytecomp-that-one'.
Until fairly recently (revision 94414) the symbols `this-kind' and and
`that-one' were present in the bytecomp.el
There is a comment about this which says:
,----
| ;; The `bytecomp-' prefix is applied to all local variables with
| ;; otherwise common names in this and similar functions for the sake
| ;; of the boundp test in byte-compile-variable-ref.
| ;; http://lists.gnu.org/archive/html/emacs-devel/2008-01/msg00237.html
| ;; http://lists.gnu.org/archive/html/bug-gnu-emacs/2008-02/msg00134.html
| ;; Note that similar considerations apply to command-line-1 in startup.el.
`----
The symbols (this-kind and that-one) appear to have been changed here:
,----
| ------------------------------------------------------------
| revno: 96701
| committer: Glenn Morris <rgm@gnu.org>
| timestamp: Thu 2009-07-23 02:53:29 +0000
| message:
| (byte-compile-from-buffer, byte-compile-output-file-form)
| (byte-compile-output-docform, byte-compile-file-form-defmumble)
| (byte-compile-output-as-comment):
| Give some more local variables with common names a "bytecomp-" prefix,
| so as not to shadow things during compilation.
| ------------------------------------------------------------
|
| ------------------------------------------------------------
| revno: 96702
| committer: Glenn Morris <rgm@gnu.org>
| timestamp: Thu 2009-07-23 02:54:00 +0000
| message:
| (load-time-value): Update for the name-change `outbuffer' to
| `bytecomp-outbuffer'.
| ------------------------------------------------------------
|
`----
Revision 96701 renamed the `byte-compile-file-form-defmumble's local vars:
`this-kind' -> `bytecomp-this-kind'
`this-one' -> `bytecomp-this-one'
`that-one' -> `bytecomp-that-one'
`outbuffer' -> `bytecomp-outbuffer'
Revision 96702 renamed the `load-time-value' local var:
`outbuffer' -> `bytecomp-outbuffer'
but it appears to have left the `this-one' and `this-kind' vars unchanged.
Unless I am misunderstanding/missing something either:
a) some special magic that happens invisibily when Emacs is dumped and the
current constraint is some sort of backward compatibility kludge;
b) the macro never worked correctly;
c) revisions at 96701/96702 created a bug where `load-time-value's can no longer
alter via fset the function cell of `byte-compile-file-form' because the
following constraint can not be satisfied;
d) the macro never worked correctly and revisions at 96701/96702 created an
additional bug;
My money is on d.
Right now if the macro is change to have the following form instead:
(and (fboundp 'byte-compile-file-form-defmumble)
(boundp 'bytecomp-this-kind) (boundp 'bytecomp-that-one))
`byte-compile-file-form' _can_ get rebound and this is not good. Moreover, even
with this (further breaking) change I am not able to obtain the behavior
described in the manual at: (info "(cl)Time of Evaluation")
Is there some reason why the entire inner branch can't be elided with the macro
written as:
,---- (lightly tested)
|
| (defmacro load-time-value (form &optional read-only)
| "Like `progn', but evaluates the body at load time.
| The result of the body appears to the compiler as a quoted constant."
| (if (cl-compiling-file)
| (print `(set ',(make-symbol "--cl-load-time--") ,@form)
| (symbol-value 'bytecomp-outbuffer))
| `(eval ',form)))
|
`----
Also, what does the READ-ONLY arg do?
The only possibility I can think of is that it somehow dovetails with the
:read-only key in defstruct.
--
/s_P\
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