Re: safe_call1 considered harmful

[Kenichi Handa <handa@m17n.org>]

In article <uac73gdpy.fsf@gnu.org>, Eli Zaretskii <eliz@gnu.org> writes:

>> But, by considering this problem again, I found another
>> solution than calling find-operation-coding-system with
>> (FILENAME . BUFFER).  That is to provide an extra argument
>> BUFFER.  Then, we can keep backward compatibility and
>> find-buffer-file-type-coding-system works as before, and, by
>> modifying po-find-file-coding-system to check that extra
>> argument instead of checking if FILENAME is cons or not, we
>> can make it work well too.

> This will work if no function on file-coding-system-alist currently
> looks at arguments beyond the 1st one, the file name.  If there are
> functions which look beyond that, such a change will break them.

No, what I meant is to give the extra argument BUFFER at the
END of the normal arguments to insert-file-contents.  So,
for instance, tar-extract will call
find-operation-coding-system as this:

			     (car (find-operation-coding-system
				   'insert-file-contents
				   name t nil nil nil (current-buffer)))

The new docstring (only the last paragraph) for
find-operation-coding-system will be:

----------------------------------------------------------------------
[...]
If OPERATION is `insert-file-contents', there may be an extra argument
BUFFER at the end.  In that case, FILENAME is a file name to look up,
and BUFFER is a buffer that contains the file's contents (not yet
decoded).  If `file-coding-system-alist' specifies a function to call
for FILENAME, that function should examine the contents of BUFFER
instead of reading the file.
----------------------------------------------------------------------

This change breaks only such a function that checks that the
number of given arguments is not greater than 5 (the maximum
arguments to insert-file-contents).  I believe such a
function is very very rare.

> In any case, I think we should revert the change you made to use
> safe_call1.

Yes.

---
Kenichi Handa
handa@m17n.org