Re: Emacs awfully slow on some files

[Stefan Monnier]

> I have a file which is 1 MB long and all of the content is on a single
> line.  Using Emacs on this file is pretty much impossible due to the
> super-sluggish behavior.  It's embarrassing.  Why is this?

It's probably a combination of various pieces of code which make
incorrect assumptions about the expected line length.

> Can it be fixed?

Yes.

> This is with fundamental-mode, by the way.

Good: in several other modes, I could argue that such a long line is
a bug, but fundamental-mode should cater to weird files.

> `forward-char' and `backward-char' are pretty much the only usable
> commands, even "C-h f" (describe-function) is extremely slow in
> this scenario.

Please report a bug for it via M-x report-emacs-bug, and ideally include
some recipe (in case it depends on the actual content of the long line,
for example, or if it needs more than "emacs -Q" to reproduce).


        Stefan