Visual selection clipped to 250000 characters in file with long lines

[bcc32]

Issue type

• Bug report

Environment

Emacs version: GNU Emacs 30.1.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 1.15.12, Xaw scroll bars) of 2025-02-24
Operating System: Rocky Linux 8.10 (Green Obsidian)
Evil version: Evil version 1.15.0
Evil installation type: NonGNU ELPA
Graphical/Terminal: Graphical
Tested in a make emacs session (see CONTRIBUTING.md): Yes

Reproduction steps

• Start Emacs (make emacs)

• Open a file with very long lines. I started with a 15MB or so text
  file with large tables. Maybe some large CSV would work here.

  I believe it is sufficient to use a file where
  (long-line-optimizations-p) would return non-nil and whose size is
  greater than 500000 characters.

• C-x h y

• In a new empty buffer, press p

Expected behavior

The whole first file's contents should be pasted into the new buffer.

After C-x h is pressed in the first buffer, (region-end) returns 250,001.

Actual behavior

Only the first 250,000 characters are copied.

After C-x h is pressed in the first buffer, (region-end) should
return the number of characters in the file, plus one.

Further notes

Moving the selection around and trying to expand it by hand does not
help; the size of the selection stays consistently around 250,000
characters even as the bounds move forward and back through the
buffer.

long-line-optimizations-region-size defaults to 500,000. According
to its docstring, for buffers where (long-line-optimizations-p) is
non-nil, pre-command-hook and post-command-hook are executed on a
narrowed buffer, whose narrowed region size is specified by this
variable.

However, just setting this variable to avoid the restriction seems to
be not recommended, according to its docstring.