knitr code chunks in footnotes

Question

My issue is to include verbatim output from knitr Sweave code chunks in footnotes. The BVerbatim environment (fancyvrb) gives me the formatting that I want. (NB: one needs to put \VerbatimFootnotes somewhere following the preamble.) With the chunk option results='asis' the code is delimited with \begin{Sinput} ... \end{Sinput}. Is there a way to ensure that these do not appear, or to omit them? An example is at the end of the post.

If I include the output directly in the footnote, whether with results='asis' or results='markup', the formatting is untidy and the code appears normalsize, even if I have size='footnotesize' as a chunk option. I can of course admit defeat and include the code directly in a BVerbatim environment, with the concurrent risk that the code that is printed is not guaranteed to be the code that is executed.

\documentclass{article}
\usepackage{fancyvrb}
\begin{document}
\VerbatimFootnotes
<<setup, echo=FALSE>>=
render_listings()
@

<<install-pkg, echo=FALSE, eval=FALSE>>=
repos <- "http://cran.csiro.au"
install.packages('httr', repos=repos)}
@ 

To install the package {\em httr}, execute
the code in the footnote.\footnote{
\begin{BVerbatim}[baseline=t]
<<install-pkg, eval=FALSE, echo=TRUE, results="asis">>=
@ 
\end{BVerbatim}
}
\end{document}

Answer 1

The following is clumsy, but achieves what I want

    \documentclass{article}
    \usepackage{fancyvrb}
    \begin{document}
    \VerbatimFootnotes
    \newcommand*\FancyVerbStopString{'zzz'}
    <<setup, echo=FALSE>>=
    render_listings()
    @

    <<install-pkg, echo=FALSE, eval=FALSE>>=
    repos <- "http://cran.csiro.au"
    install.packages('httr', repos=repos)}
    @ 

    To install the package {\em httr}, execute
    the code in the footnote.\footnote{
    \begin{BVerbatim}[baseline=t, firstline=2, lastline=3] 
    <<install-pkg-fn, eval=FALSE, echo=TRUE, highlight=FALSE, results="asis">>=
    <<install-pkg>>
    'zzz'
    @ 
    \end{BVerbatim}
    }
    \end{document}

The effect of firstline=2 is to drop off the \begin{Sinput}. One could specify lastline=3 to drop off the \end{Sinput}. However, for automatic use, this requires a mechanism for counting the number of lines of code. Hence the use of

        \newcommand*\FancyVerbStopString{'zzz'}

Of course, any alphanumeric character string will do in place of 'zzz'