206 C++
- Your code is more likely to run at maximum efficiency on many dif-
ferent platforms in many different configurations.
C++ users, alas, are forced to pick up their garbage manually. Many have
been brainwashed into thinking that somehow this is more efficient than
using something written by experts especially for the platform they use.
These same people probably prefer to create disk files by asking for platter,
track, and sector numbers instead of by name. It may be more efficient
once or twice on a given configuration, but you sure wouldn’t want to use a
word processor this way.You don’t even have to take our word for it. Go read The Measured Cost of
Conservative Garbage Collection by B. Zorn (Technical Report CU-CS-
573-92, University of Colorado at Boulder) which describes the results of a
study comparing performance of programmer-optimized memory manage-
ment techniques in C versus using a standard garbage collector. C pro-
grammers get significantly worse performance by rolling their own.OK, suppose you’re one of those enlightened C++ programmers who wants
a garbage collector. You’re not alone, lots of people agree it’s a good idea,
and they try to build one. Oh my, guess what. It turns out that you can’t add
garbage collection to C++ and get anything nearly as good as a language
that comes with one built-in. For one thing, (surprise!) the objects in C++
are no longer objects when your code is compiled and running. They’re just
part of a continuous hexadecimal sludge. There’s no dynamic type infor-
mation—no way any garbage collector (or for that matter, a user with a
debugger) can point to any random memory location and tell for sure what
object is there, what its type is, and whether someone’s using it at the
moment.The second thing is that even if you could write a garbage collector that
only detected objects some of the time, you’d still be screwed if you tried
to reuse code from anyone else who didn’t use your particular system. And
since there’s no standard garbage collector for C++, this will most assur-
edly happen. Let’s say I write a database with my garbage collector, and
you write a window system with yours. When you close one of your win-
dows containing one of my database records, your window wouldn’t know
how to notify my record that it was no longer being referenced. These
objects would just hang around until all available space was filled up—a
memory leak, all over again.