Re: Garbage collection in C++

James Kanze <>
Wed, 19 Nov 2008 06:05:45 -0800 (PST)
On Nov 19, 3:32 am, Sam <> wrote:

James Kanze writes:

On Nov 18, 1:18 pm, Sam <> wrote:

James Kanze writes:

On Nov 18, 12:40 am, Sam <> wrote:

Garbage collection is as useful for C++ as a fifth leg
would be useful to a dog. A dog with five legs might
find some use for the extra one, but most of the time it
would just get in the way.

Another ridiculous analogy, which doesn't relate to anything.

Really? What exactly is so ridiculous about it.

Because it doesn't relate to anything.

It relates perfectly to an attempt to shoehorn a
garbage-collection based paradign into a language that's not
designed for it.

Except that it fits perfectly into the philosophy of the

                                         A dog isn't like a
program, and a fifth leg has nothing to do with garbage

Neither does garbage collection have anything to do with C++.

Obviously, you don't understand C++, in order to say that.

Really. Every one I've talked to who's used the Boehm
collector has found it useful.

You cannot extrapolate such a small sample to the world at

Do you have any other sample to work with. I'm not aware of any
other garbage collector.

Your sample of a small subset of inexperienced developers,

On the contrary, inexperienced developers generally don't
realize that C++ can have garbage collection. And an
inexperienced programmer will not be able to install the Boehm
collector on his machine.

who lack the ability to properly design a complicated C++

Except that they've properly designed any number of complicated
C++ applications.

is not a representaive sample of a majority of C++ developers
who know how to keep track of their objects, and know what
they're doing.

So what is your sample? Where are all these experienced
programmers who've used garbage collection in C++, and found it

* Forget about having a proper design. Just start allocating
globs, left and right, and rely on the garbage collector to
clean up after you. This is really a sign of a naive and
inexperienced developer.

Obviously, some one who doesn't know software engineering.

Proper software engineering, in C++, is inapposite of garbage

Not according to the experts. Those who know what they're

* There's nothing I like more than my application grinding to
a halt, while the garbage collector scans the heap for

Obvously, soe one who doesn't know how garbage collection
works today.

I see. The garbage collector identifies unreferneced objects
by magic, with zero cost of CPU time.

Nothing has zero cost. In many systems, the runtime cost of
garbage collection is inferior to that of manual memory

Wonders never cease.

Actual concrete measurements neither. But facts don't seem to
interest you very much.

A garbage collector is not a tokenizer and not a compiler.
Both of these tools do what cannot be done efficiently in
other ways.

And how is a garbage collector different.

Because you can always engineer a better implementation,
without the garbage collector, that's more memory efficient,
and runs faster.

Can you? Prove it. And prove that it's worth the extra effort.

                                            Without these tools,
you can certainly get the job done, but you need to write more
code to do it.

Sometimes there's no substitute for the real thing. In other
words, what you're saying right here, is that garbage
collection lets you cut corners. You are incapable of putting
together a proper design, so you have to put up with the extra
overhead of garbage collection, in order to get something that

Are you really this stupid, or is this just a troll. Delivering
quality software on time and on budget is NOT cutting corners.
Not using a tool which would reduce cost and increase quality is
exceedingly unprofessional.

There's nothing some garbage collector does can do that
cannot be done using proper design, methodology, and
programming practices.

And a bit of extra work. Exactly. There's also nothing
that flex can do that cannot be done using proper design,
methodology and programming practice.

You obviously do not understand flex. Unlike garbage
collection, flex does not impose a significant penalty, in
terms of memory and CPU usage.

You obviously don't understand software engineering. It's not
difficult to produce a tokenizer by hand that uses significantly
less memory that flex, and is faster. Most of the time, it's
just not worth it. Ditto garbage collection, except that it's
far from obvious how to produce code which is faster than it, at
least for some applications.

to implement something properly. Well, I suppose, but
sometimes one needs to spend the appropriate amount of time
to do things right. It's an investment well spent.

Hacking out code to solve an already solved problem is not an
investment well spent.

Garbage collection does not solve any problems. Except of
laziness, of course, and lack of experience. It cause more
problems than it purports to solve.

Which is blatently false, of course. Statements like that just
prove your incompetence. (Of course, you tend to prove it a lot


Than proper C++ code that's designed correctly, by someone who
knows what he's doing.

Well, if he really knows what he's doing, he's got the Boehm
collector in his tool box, and will use it when it's

Which, so far, appears to be never.

That is a provable false statement (like most of yours). Lot's
of people are using garbage collection, with C++, in real
applications. It works.

C++ has no appropriate use for garbage collection. If there
was one, it would be a part of the language.

That's the most ridiculous statement I've heard to date.
Originally, C++ didn't have templates, thus, there was no
appropriate use for templates. Originally, C++ didn't have
multiple inheritance, so there was no appropriate use for
multiple inheritance. And what next: no appropriate use for
classes, since C didn't have them?

But it's not. For the simple reason that, unlike with Java,
you cannot have accurate garbage collection in C++.

That is about to change. And you can have mostly accurate
garbage collection, even with C.

Indeed. The Sun approach. Throw gobs of memory at the
problem, and hope that it goes away.

It's not gobs, and it's not a vain hope. Using garbage
collection reduces the number of lines of code needed to
write a correct application.

A correct application does not leak memory, with the
expectation that a garbage collector will clean it up.

A correct application does what it is supposed to do. Using
whatever means are appropriate. A correctd application doesn't
renounce using some specific tool just because the developer
wanted to prolongate his contract by making extra work for
himself, or was too dumb to analyse correctly the effects of
various tools, just because he's never used them before.

                     Even more, it reduces the effort required,
since I don't have to choose which smart pointer to use where.

In other words, you don't have to be as smart, if you use
garbage collection in lieu of proper class design, right? In
other words, "C++ for dummies".

More stupidity from you. Now, apparently, you don't even know
how to read English. Or do you consider it "smart" to
artificially increase the amount of work you have to do? (Maybe
to extend your contract? Maybe it's not stupidity on your part,
but just dishonesty.)

Now I understand why people were so amazed when I managed
to produce an XML-database gateway, in C++, that consumed
less than a hundred or so of heap, per process instance.

Which doesn't say anything. If you're using a SAX based parser,

It had nothing to XML parsing. The overhead of XML parsing
using any approach is dwarfed by the overhead of supporting a
database connection.

Obviously, you're not too familiar with everything that can be
done in XML (or the usual terminology surrounding it).

Apparently, wasting time worrying about things that don't
matter isn't unknown yet. There are times when your memory
use footprint is important, and there are times when it
isn't. Whether my application uses 100KB (without garbage
collection) or 200KB (with) really doesn't interest my boss
as much as how much time I need to produce it.

Well, it should. It should certainly interest him in knowing
whether the same hardware will simultaneously support half as
much users or clients than a properly-designed client.

Should it? What should interest him is how to support the
number of users or clients he has to support, at the lowest
price and the highest quality. If your application is I/O
bound, then throwing man-months of extra programming work at it,
fruitlessly trying to improve performance, is not cost

And just because I have sufficient resources to support a
sloppily-written client that relies on garbage collection is
not a valid excuse for producing one.

Experienced managers understand that spending the time in
doing things right is the proper thing to do.

Competent managers know that throwing money out the window to
implement things that have already been implemented is not the
proper thing to do.

James Kanze (GABI Software)
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