Footnotes running off edge of page

Question

When using long section titles and the para option from footmisc, the footnotes are pushed off the edge of the page. E.g.

\documentclass{article}
\usepackage{lipsum}
\usepackage[para]{footmisc}
\begin{document}
    \section{This is a very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very long section title.}
        This is some text.\footnote{\lipsum[1-6]}
        \lipsum
\end{document}

Remove the para option to see the difference. How can I prevent the footnote from extending below the text boundaries?

Answer 1

Run-in (paragraph) typesetting of footnotes in (La)TeX is tricky. An introduction to the problems faced is section 9 of the documentation of the manyfoot package. With regard to the algorithm of footmisc, its para option needs to "mess about with the output routine" (footmisc documentation, p. 12). Page 13 of the footmisc manual states:

We make a box out of the paragraph of footnotes, and then stuff the contents of the box into that which is going to be \shipped out.

Although I'm not familiar enough with LaTeX's output routine to be sure, I suspect that the "box" referred to simply can't be broken across pages.

Solution: Replace footmisc with the bigfoot package which features the most advanced algorithm for run-in footnotes.

\documentclass{article}
\usepackage{lipsum}
\usepackage{bigfoot}
\DeclareNewFootnote[para]{default}
\begin{document}
    \section{This is a very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very long section title.}
        This\footnote{Yes,} is\footnote{it is} some\footnote{indeed.} text.\footnote{\lipsum[1-6]}
        \lipsum
\end{document}