Here's how I'd do it with my PythonTeX package, which uses the Python Pygments library for highlighting. The PythonTeX package provides a listings environment, using newfloat. I've created a command \codeline that allows you to insert references to specific lines of code in the list of listings as well. \codeline must only be used in comments, so that it will be processed (automatically and correctly) during code highlighting. Also, for it to work properly, you must give each listing a caption before actually entering the code (otherwise, the order in the list of listings is off).
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\documentclass{article}\usepackage[pygopt={texcomments=true,style=emacs}]{pythontex}\setpythontexlistingenv{listing}\newcounter{sublisting}[listing]\newcommand{\codeline}[1]{% \addcontentsline{lopytx}{listing}% {\protect\numberline{\hspace{0.5in}\thelisting.\arabic{FancyVerbLine}}\hspace{0.5in}#1}%}\begin{document}\listoflistings\begin{listing}[h!]\caption{Hello, world}\begin{pygments}[numbers=left]{c++}# include <iostream>int main(){ std::cout << "Hello, world!\n"; //\codeline{Important code line!}}\end{pygments}\end{listing}\begin{listing}[h!]\caption{Hello, world, again!}\begin{pygments}[numbers=left]{c++}# include <iostream>int main() //\codeline{Another important line}{ std::cout << "Hello, world!\n"; }\end{pygments}\end{listing}\end{document}