next-error wrong position in target file

[Kevin Ryde]

In Emacs 22.2, the first `next-error' in certain circumstances goes to
the wrong error line in the target file.  With the dummy file foo.txt
below, and on a 50 line console,

    emacs -Q foo.txt
    C-v               # page down in foo.txt
    C-x b Ret         # back to *scratch* buffer
    M-x compile
    echo 'foo.txt:''150: an error here'
    C-x `             # next-error

    => goes to foo.txt with point at line 56

The echo simply produces a compilation buffer claiming an error at
foo.txt line 150, but then next-error goes to line 56.  On a different
size terminal or under X you get a different wrong position, like line
45 or 24.

The recipe above is rather specific, there's all sorts of ways it works
correctly.  If you don't scroll-up, or if you leave foo.txt the current
buffer, then it's fine.  I've struck this on various occasions without
ever being able to reproduce it, since a second try in the same session
goes ok!  My recent-ish build of the current emacs cvs head still seems
to have the problem too, whatever it is.



In GNU Emacs 22.2.1 (i486-pc-linux-gnu, GTK+ Version 2.12.3)
 of 2008-04-11 on raven, modified by Debian
configured using `configure  '--build=i486-linux-gnu' '--host=i486-linux-gnu' 
'--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' 
'--localstatedir=/var/lib' '--infodir=/usr/share/info' 
'--mandir=/usr/share/man' '--with-pop=yes' 
'--enable-locallisppath=/etc/emacs22:/etc/emacs:/usr/local/share/emacs/22.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/22.2/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/22.2/leim'
 '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 
'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g 
-O2''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_AU
  locale-coding-system: iso-8859-1
  default-enable-multibyte-characters: t

foo.txt
Description: Text document