Stripes in background color drawn by listings package

Question

I'm trying to create a verbatim environment with a colored background and which can span across pages (so using a colorbox is not an option). It seemed that the listings package was a good way towards it, but the background is drawn one line at a time, such that, when I view the PDF, I see annoying white-ish "stripes" between the lines as well as where the invisible (0pt) frame rule was not to be drawn:

Here's the minimal code I used to create the output shown in the image:

\documentclass{minimal}
\usepackage[pdftex]{xcolor}
\usepackage[a4paper,hmargin=6cm]{geometry}
\usepackage{listings}
\lstset{backgroundcolor=\color{gray},
  frame=single, framerule=0pt, framesep=5pt}
\begin{document}

\begin{lstlisting}
 if (a < b)
 {
    printf("A is smaller than  B!\n");
 }
 a = b;
\end{lstlisting}

\end{document}

Is there any workaround against these 'stripes'?

Answer 1

A simple workaround would be to not specify a color for the listings themselves, put instead use a \colorbox, but for that to work, you either need to use \lstinputlisting or store the result in a box using e.g. lrbox.

\newbox{\mybox}
\begin{lrbox}{\mybox}
\begin{minipage}{\linewidth}
\begin{lstlisting}
 if (a < b)
 {
    printf("A is smaller than  B!\n");
 }
 a = b;
\end{lstlisting}
\end{minipage}
\end{lrbox}
\colorbox{gray}{\usebox{\mybox}}

UPDATE: However, a more beautiful solution is to use Donald Arseneau's framed.sty, which also allows the source-code to span multiple pages.

\documentclass{minimal}
\usepackage[pdftex]{xcolor}
\usepackage[a4paper,hmargin=6cm]{geometry}
\usepackage{listings}
\usepackage{framed}
\begin{document}

\definecolor{shadecolor}{named}{gray} 
\begin{shaded}
\begin{lstlisting}
 if (a < b)
 {
    printf("A is smaller than  B!\n");
 }
 a = b;
\end{lstlisting}
\end{shaded}

\end{document}

Answer 2

Which PDF viewer do you use? Did you zoom in and still see the lines? Do they show in a printout? In many cases thin lines are just an artifact of the PDF viewer.