One of the quintessential UNIX tools is the grep tool. The global regular expression print is a tool that prints lines of text file that match a given regular expression. In this post we will apply JIT compilation to a very simple regular expression matcher by Rob Pike.

A just-in-time (JIT) compiler is a compiler that in contrast to the usual compilers is not run ahead-of-time, i.e. before running the actual program, but during the program itself.

In the last chapter, we extended our plugin so it was possible to visualize the control flow graph of a function. In this chapter we will reach our goal to warn unused results of function calls.

In the last post we set up everything in order to write a GCC plugin. Before we can go on we need to understand a bit how GCC compiles your files.

GCC's C and C++ compilers provide several extensions to address several programming needs not covered in the standards. One of these is the warn_unused_result attribute. This attribute warns us that we are discarding the result of a function. Unfortunately, for C++ it does not always work as expected.