Re: ediff-files uses wrong coding system for temporary file

[Joe Wells]

Has anyone else been able to reproduce this bug?

Joe

Joe Wells <jbw@macs.hw.ac.uk> writes:

> To reproduce:
>
> 1. Pick a UTF-8-encoded file with lots of non-ASCII characters.  (For
>    example, you can pick “latin-ltx.el” from the Emacs distribution.)
>    Assume for the sake of discussion that this file is named “X”.
>
>    This file should be uncompressed.  (If it is compressed, adjust the
>    following instructions to make an _uncompressed_ copy of it.)
>
> 2. Copy this file to a fresh name:
>
>      cp X /tmp/Y
>
> 3. Compress the copy:
>
>      gzip /tmp/Y
>
> 4. Start a fresh Emacs:
>
>      emacs -Q
>
> 5. Use ediff-files on the original file and its compressed copy:
>
>      M-x ediff-files RET X RET /tmp/Y RET
>
> 6. Observe many differences reported, despite the fact that the files
>    should be considered identical.
>
> The cause of the problem is that Ediff uses ediff-make-temp-file to
> make a temporary uncompressed version of the compressed file to use as
> input to “diff”.  It uses the value of ediff-coding-system-for-write
> for the coding system when writing this temporary file.  The value of
> ediff-coding-system-for-write at this point in time differs from the
> coding system of the original file.  It should probably instead use
> the coding system of the compressed file.
>
> I hope this report is helpful.
>
> Joe
>
> ======================================================================
> In GNU Emacs 22.1.1 (i686-pc-linux-gnu, GTK+ Version 2.8.20)
>  of 2007-06-27 on artemis
> Windowing system distributor `The X.Org Foundation', version 11.0.70000000
> configured using `configure  '--prefix=/home/jbw/local2' '--enable-debug' 
> '--disable-nls' '--with-x-toolkit=gtk' 'CFLAGS=-O0 -g3 -ggdb''
>
> Important settings:
>   value of $LC_ALL: nil
>   value of $LC_COLLATE: nil
>   value of $LC_CTYPE: en_US.UTF-8
>   value of $LC_MESSAGES: nil
>   value of $LC_MONETARY: nil
>   value of $LC_NUMERIC: nil
>   value of $LC_TIME: jbw
>   value of $LANG: nil
>   locale-coding-system: utf-8
>   default-enable-multibyte-characters: t
>
> Minor modes in effect:
>   shell-dirtrack-mode: t
>   outline-minor-mode: t
>   desktop-save-mode: t
>   url-handler-mode: t
>   partial-completion-mode: t
>   tooltip-mode: t
>   mouse-wheel-mode: t
>   file-name-shadow-mode: t
>   global-font-lock-mode: t
>   font-lock-mode: t
>   blink-cursor-mode: t
>   unify-8859-on-encoding-mode: t
>   utf-translate-cjk-mode: t
>   auto-compression-mode: t
>   temp-buffer-resize-mode: t
>   size-indication-mode: t
>   line-number-mode: t
>   transient-mark-mode: t