# Can anyone explain why setting \lineskiplimit breaks align?

OK, so this is a follow-up to one of my previous questions:

If you uncomment the \lineskiplimit line, LaTeX goes crazy. Why? Does anyone have an idea how to fix it (without manually changing \lineskiplimit temporarily, or hacking into amsmath, which seems a bit nightmare-ish)?

\documentclass{article}

%\lineskiplimit=-\maxdimen
\usepackage{amsmath}

\begin{document}
A sample aligned equation:
\begin{align*}
c^2&=a^2+b^2
\end{align*}
\end{document}

-

Here you find one of the reasons: amsmath.sty says

\def\@display@init#1{%
\everycr{%
\noalign{%
#1%
\ifdt@p
\global\dt@pfalse
\vskip-\lineskiplimit
\vskip\normallineskiplimit
\else
\penalty\@eqpen \global\dspbrk@lvl\m@ne
\fi
}%
}%
}


and this of course has quite a bizarre consequence:

Overfull \vbox (15864.60002pt too high) has occurred while \output is active


It's not a good idea to set \lineskiplimit=-\maxdimen except in very controlled situations such as tabulars where struts can be inserted (and are, actually).

-
Thanks, but what sense does it make to \vskip -\lineskiplimit and then \normallineskiplimit!? – mbork Mar 24 '12 at 22:15
OK, I guess I understand: the second one may get discarded, and we might want exactly this. So what should I do if I actually want a negative \lineskiplimit in my document? Any idea? – mbork Mar 24 '12 at 22:18
OK, so I asked this in a separate question. – mbork Mar 24 '12 at 22:34
Link to the new question – 黄雨伞 Feb 6 at 15:27