Frequently Asked Questions

What do you have against (G)ZDoom?

I became a competitive player on ZDaemon 1.08 (which was derived from ZDoom 1.23b33), and it is insanely fun to play; it might be the most fun I’ve ever had playing a game. My argument against ZDoom and ZDoom-derived ports is not that they aren’t fun or that they’re bad; I think they’re tons of fun and pretty amazing. I am dismayed that ZDoom and its derivatives are what people think of as “Doom”, when they are really entirely different engines that just happen to load Doom resource files. What follows is heavy-handed, sharp criticism of ZDoom, and while it may seem like I have a grudge against its developers, in truth I respect and even like them. That said, here we go :) .

ZDoom is in no way compatible with Doom demos. It hasn’t been for years. Furthermore, ZDoom breaks compatibility with its own demos haphazardly. One of Doom’s strengths is its rich history, and ZDoom has no regard for preserving it.

ZDoom’s physics and renderer are also drastically different than Doom’s, and it isn’t possible to configure them to revert to original settings, because vanilla behavior is not a priority for ZDoom developers. Even the super-shotgun spread was changed. Such changes have huge effects on competitive play, but this is also not a priority for ZDoom developers.

ZDoom’s licensing is restricted to non-commercial use only, which limits the venues where Doom could expand. It also allows closing of the source code, which has nearly destroyed the Doom community. There are several parts of the codebase which, over the years, have illegaly incorporated code licensed under incompatible licenses (Quake, for example). ZDoom’s popularity is largely due to these incorporations, either illegal or under restrictive licenses, and has therefore come at the expense of the Doom community as a whole. Modders were left with a choice between proprietary, restricted ZDoom or an open port with fewer features, and as a result, the lion’s share of Doom mods rely on proprietary ZDoom features.

ZDoom continues to use features and code from non-free libraries and codebases, most infamously FMOD and BUILD. However, to their credit, ZDoom developers freely release their original code under the 2-clause BSD license, which, even though it allows the source to be closed, at least offers other source port developers the chance to incorporate those features in open ports.

ZDoom’s scripting language, ACS, is a nightmare. It is a terrible, weak scripting language requiring a custom VM. Instead of responsibly using a proper, 3rd party scripting language, ZDoom chose to extend ACS (first included by Hexen). Because of ZDoom’s popularity, the de facto Doom scripting language is ACS and the default level of ACS support is whatever ZDoom supports. Coupled with the fact that until 2008, ACS could not be included in GPL source ports due to its restrictive licensing, ZDoom essentially monopolized Doom scripting with a proprietary, substandard language.

Finally, ZDoom’s code style is inconsistent, at times unreadable, and often downright dangerous.

What do you have against C++?

C++’s templates and better type-safety are clear improvements over C. However, C++ incorporates four major misfeatures that, even though they are technically optional, you must use if you wish to interact with any 3rd party code. Altogether, these misfeatures outweigh C++’s advantages over C.

Object-Oriented Programming

OOP is centered around three major ideas: polymorphism, encapsulation, and inheritance. Polymorphism is just a different placement of the business logic dispatch, encapsulation is just a different (worse) placement of the object state, and inheritance is unnecessary and harmful. Even worse, OOP is slow.

Programmers often conflate powerful type systems with OOP, but there are type systems even more powerful than that of C++ and Java in languages that do not support OOP. And importantly, despite C++’s improved type system, programs written using it continue to have type errors.

The downside of OOP is that it lends itself far too easily to over-engineering and complexity. Very rarely are object hierarchies – or even objects themselves – needed. C++’s implementation comes with all sorts of baggage; move semantics, const methods, etc. etc.

OOP is simpler for novice programmers to understand, and it’s possible that in a huge codebase it can improve productivity (although I doubt it, see the Linux kernel for a good example otherwise). However, that benefit alone is not worth the ocean of complexity it requires.


Exceptions disrupt the entire control flow of your program and are difficult to reason about. This can be mitigated with checked exceptions, Java is an example of this, but the try/catch syntax is burdensome, and developers consequently let them become crashes rather than deal with them.

Operator Overloading

Operator overloading produces code that is impossible to understand, as one cannot know what the code actually does. The only case for operator overloading is implementing additional numeric types, and support for this should be added at a lower level.

The Standard Template Library

While usually well-implemented and very useful, the STL is wildly over-verbose and renders any application that uses it too complex to really use. In fairness, this is because C++’s facilities for implementing generics are over-verbose, but this is a criticism of C++, so the point is valid.

What do you have against Microsoft Visual C++?

MSVC++’s support for C is substandard, and their response to this charge is “use C++”. That answer doesn’t satisfy me, for the aforementioned reasons.

Why did you fork PrBoom+? Don’t you like Entryway?

I chose PrBoom+ for its OpenGL renderer, uncapped framerate, near-perfect compatibility with several historical source ports, GPL license, and its C codebase.

Entryway is obviously way smarter than me, which is why I chose to build upon his (not to mention the dozens of other contributors to PrBoom) work. It would have taken me years to solve the problems he’s solved, presuming I’m even skilled enough to do so. I don’t mean this fork as an insult, I mean it as a compliment :).