Rants on software, computing, and any other topic I feel like.

Tuesday, May 17, 2005

Writing C in C++

I’m sure that you’ve heard of the term C/C++ as if somehow they are so interrelated that they can combined into a single term. C and C++ are about as close as a lilac bush and George Bush. Sure they share some of the same terminology but you wouldn’t want to meet one of them in a dark alley at night.

C is good for one thing, being one step above assembly code. Anyone who tells you otherwise is lying to themselves. Everything about C is about making things you do in assembly easier. The perfect example is the switch statement. There is no rational reason to force the programmer to put break statements at the end of every case. It doesn’t make any sense unless you know that the switch statement is likely to be implemented using jump opcodes. Also, who in their right mind uses up an entire operator to implement bit shifting?! Unless you’re some sort of divide-with-shifts freak, then you’re just not going to use them very often.

And why do they call them function pointers? There’s no reason that the user should have any idea how functions are implemented, let alone knowing that they can be pointed to. The syntax for function pointers is bad enough.

C is a great language for compiler writers. For every construct in C, there is a fairly straightforward translation to assembly. This is of course the main issue behind all the complaints about C. It wasn’t designed to be a language, it was designed to easily translated. So it shouldn’t come as much of a surprise to learn that the guys who came up with templates never wrote a compiler. Sure, they took a class on compilers, but that doesn’t mean that learned to love their local compiler guy. Really, who complains the loudest about how hard it is to implement templates in C++? Compiler writers. More specifically, Microsoft’s compiler writers who proved that templates are hard by producing Visual C++ 6.0 where using templates is like trying to teach your dog new tricks only to find out that it is an armadillo. Sure an armadillo looks like a dog, but partial function template specialization looks likes it might work. But it just doesn’t. Whether you like it or not.

C++ is a boon to the programming world. It took C places way beyond where the compiler writers wanted to go, which is a good thing. When people start complaining about something, it’s usually a good sign that something is getting done. C++ doesn’t make any effort to be nice to compiler writers. This made getting Visual C++ done take way longer than Microsoft Bob, but it sure makes for a flexible language. Compiler writers don’t like that word, flexible. It means that they have to work. They have to work to take all the flexibility into account. But I don’t care, I’m not a compiler writer.

Someone invented C so they wouldn’t have to code in assembly, and someone invented C++ so they wouldn’t have to code in C. So if you’re a C programmer writing C in C++, then you’re basically installing an automatic garage door opener and then opening the door by driving into it. You’re not using the features of the language that you claim to embrace. Here are some of the features that C in C++ programmers tend to continue to use even thought C++ has surmounted their craziness.

First, function pointers. Virtual functions were invented so you freaks using function pointers could stop the madness. If you’re using a function pointer as a callback, then use virtual functions. They’re easier to use, more flexible and the syntax doesn’t look like monkey spew. There are numerous other reasons to use virtual functions beyond callbacks, so for those of you who think that function pointers are God’s gift, they’re more like Satan’s spawn.

Second, typedef’ed structs. Newsflash, typedef’ed structs are no longer necessary. You wouldn’t be using them in C++ if you knew why you had to use them in the first place. A struct is now an actual type. That was the whole point of C++. Making classes and structs act like native types. Along with this is the flawed belief in the difference between structs and classes. Repeat this mantra every morning in the shower if you still think that stucts and classes have some fundamental difference, “A class is just a struct where the default is private versus public.” There isn’t any other difference. No way, no how. Most compilers don’t even remember which is which.

Third, void pointers. They were a bad idea in C, but perhaps a necessary evil. But in C++, they’re just not at all necessary. Void pointers are not the tool of the super-hacker, they are the last resort of the design-impaired. Just because you don’t know of any other way to do what you’re trying to do with void pointers, doesn’t mean that using them is OK. It’s not OK. C++ provides so many ways to not use void pointers, that using them is a sign of your C++ ignorance. Go back ten spaces and read your beginning C++ book again.

Finally, using pointers to pass things by reference. I don’t care that you’re used to doing it this way. We just don’t pass things by pointer anymore. We pass them by reference. References are an improvement over pointers. Get over that they can’t be NULL. This is a good thing. 90% of crashes in C programs are NULL pointer dereferences. So it makes sense (yes, it actually does) that you should want to minimize the use of pointers. They don’t make you cool or more of a super-hacker because you use pointers for everything. They just make you reckless. References are safer than pointers. You don’t drive around your car without a hood just so you can have easy access to the innards when you need them. You open it as needed. Adding pointers is just like putting hood pins on a Pinto. Same goes for pointers. Use them as needed.

So what is the message here? If you’re using extern “C” at the beginning of your C++ code and telling your boss that you’re writing in C++, for all the rest of us who didn’t sleep through the nineties and have to read your over-syntaxed code, please go read a beginning C++ book and join the 21st century.

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