Programming a compiler is both fascinating and challenging. The former is fairly self-explanatory; you get to play with a variety of tools and techniques,
all of which you can apply to other areas of software development. The latter is mostly a combination of both theory and practice;
you have to understand what your compiler is doing under the hood and how you can efficiently write code to generate high-quality results.
This article will discuss some of the issues that you might face as a compiler writer and how to overcome them. It is by no means a complete guide, but can
hopefully serve as a good starting point for those who are interested in diving into this fascinating and challenging field.
Theory And Practice
When it comes to compiler writing, theory and practice are pretty much synonymous. You will, undoubtedly, spend a great deal of time studying various programming paradigms,
structures, and algorithms. However, once you understand what your compiler is doing and how it works, you can start applying your knowledge
to create the most efficient and high-quality code possible. In other words, theory and practice are not two separate entities, but rather two sides of the
same coin.
Writing A High-Quality Proof-Checker
The simplest and arguably one of the most fundamental tasks that you will have to perform as a compiler writer is to write a high-quality proof-checker.
Essentially, a proof-checker is a tool that can verify that the results that your compiler spits out are, in fact, correct. Since your compiler is writing code for you, it is rather obvious that it will not be able to
generate every possible combination of inputs; there will always be cases where it produces an incorrect result. As a result, you will have to hand-check a
subset of its output. Your proof-checker then will have to search through all of the potentially incorrect results and flag each one of them as such so
that you can investigate and fix the issue. In most cases, this will be a rather tedious process but, inevitably, necessary.
Complexity
One of the main reasons why programming a compiler is so fascinating is that it provides you with the opportunity to explore a wide variety of techniques and
tools. In most cases, this variety will be both challenging and exhilarating at the same time. One of the biggest issues that you will have to contend
with is complexity. Your compiler is, undoubtedly, going to be a rather complex piece of software. Even the most fundamental tasks such as lexing, parsing,
and semantic analysis are not simple tasks, and they form the basis of most compilers today. Naturally, this means that you are going to have to explore a
variety of complex techniques and algorithms in order to produce a high-quality product. However, this is also one of the reasons why programming a
compiler is so interesting; it allows you to specialize in areas that you are most familiar with, no matter how complex the algorithm that you are
exploring might be.
The Industry
Another important factor to consider when determining how challenging programming a compiler is, is the industry. Due to the nature of the
compiler itself, most companies that develop them are generally small to medium-sized businesses. This means that there is a limited number of potential
clients who might be interested in using your compiler. Furthermore, since these are generally short-lived projects, your client base is not going to be expanding
rapidly. In most cases, this will mean that you are going to have to be quite efficient with your coding and output in order to meet your deadlines. In
other words, the industry can be a double-edged sword; while it might be relatively ‘safe’ to program a compiler for a small business, you are most likely
not going to be able to produce the most efficient or high-quality results that you can.
Boring But Necessary
Even though most compilers are extremely useful and can save you a great deal of time and effort, not all of them are created equal. In most
cases, this is because writing a high-quality proof-checker is, itself, quite a tedious process that can take a lot of time. Naturally, this means that it
is not always a worthwhile endeavor; you have to weigh the pros and cons, and in most cases it is not worth the effort. In rare cases, you might end up
with a high-quality product that can be used for a variety of purposes. In most cases, programming a compiler is simply a case of ‘boring but necessary.’
Future
One of the most important things to consider when determining how challenging programming a compiler is, is the future. Most compilers
today are created using existing programming languages such as C++ or Java. As a result, once you become familiar with these languages, it is rather easy to
translate your knowledge into the required functionality for a compiler. Naturally, this does not mean that programming a compiler is easy; it simply means
that there is a large existing body of knowledge that you can tap into. In most cases, this is going to be both helpful and necessary.
Variety
Finally, we come to the variety part of our discussion. As we discussed above, most compilers are a rather practical application of
theory; generally, they consist of a combination of specialized tooling and carefully-planned algorithms. Naturally, this means that there is a wide variety of
issues and challenges that you are going to have to deal with. In most cases, this is going to be both helpful and stimulating, although in some cases it can
be a bit chaotic as well. Naturally, this is going to depend on the quality of the product that you are creating. In most cases, you will have to be very
careful with the planning stages of your project in order to make sure that you do not run into any unforeseen problems. In other words, variety can be both
a blessing and a curse; it can be helpful in giving you the chance to explore a variety of techniques and problems, but it can also be a huge pain in
the neck if you do not plan everything out properly.
Hopefully, the above discussion has provided you with a good idea of what writing a compiler entails. In most cases, it is simply a case of
‘boring but necessary,’ although in rare cases it can be both fascinating and challenging at the same time. In order to write a high-quality compiler,
you are going to have to be very familiar with a variety of complex techniques and algorithms. Even then, you are most likely not going to be able to avoid
the issue of complexity as you will inevitably have to search through all of the possible results that your compiler can produce in order to find the
incorrect ones. In most cases, variety will not be a problem, but in some cases it can be a blessing and in others it can be a curse. As a general rule of thumb,
if you are writing a compiler for commercial use, then plan everything out carefully and ensure that you have tested your assumptions thoroughly. In other
words, you should not underestimate how much work goes into creating a high-quality tool; it is not something that can be whipped up in a few hours that can be
used for a variety of purposes. In most cases, it is simply a matter of ‘boring but necessary’ and keeping your head down.