:: Re: [Dng] garbage collection
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Lähettäjä: Joel Roth
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Vastaanottaja: dng
Aihe: Re: [Dng] garbage collection
T.J. Duchene wrote:
>
> Hi Henrick!
>
> > There are times when garbage collection is appropriate, and times when it
> is not.
> > Most of the time it doesn't hurt, and is a great help for ensuring
> correctness.
>
> There can be an argument made for that, that is true. However, there can be
> arguments against it which are, in my mind at least, far more serious and
> compelling.
>
> 1) GC rewards and encourages bad practices.
>
> It encourages programmers to rely on the runtime for cleanup. It makes
> training programmers in proper memory management problematic when they are
> working with languages not used on the application level, e.g. assembly, C,
> C++. It trains them in a paradigm that is neither constant, nor 100%
> reliable. One of the first things that I learned in the first computer
> science course that I took years ago is that you cannot depend on the
> computer to watch itself. You must take the necessary steps to ensure
> robust correctness. Designing languages that attempt to do that for you
> creates object code that is inherently unreliable.
>
>
> 2) Major memory flaws in the GC.
>
> f there are flaws in the GC, code that would otherwise be reliable, leaks -
> eventually causing the system to crash. You can argue that any flaws in the
> runtime cause problems, I agree. The fact that GC has become a mandatory use
> feature for languages, especially proprietary ones, increases this problem
> significantly. The fact that often you cannot fix the proprietary runtime
> yourself makes matters far worse. You are literally unable to fix the
> problem, on any level, and held hostage with no way to write code that can
> at least mitigate it.
>
> 3) Resources
>
> Just having GC not using it, increases the resource requirements of the
> runtime and diminishes system efficiency significantly. This is a fact that
> no one debates. GC creates significant overhead. By having GC, you have
> to depend on it to release resources so that they can be reused, and might
> have to wait. It's called "late deallocation". You never know precisely
> when resources are released to the OS, which makes planning to using the
> absolute minimum resources impossible. They are never released immediately,
> and can lead to system exhaustion scenarios that you cannot predict.
>
>
> 4) Problem/Solution Paradox.
>
> GC was created to solve a problem, that it literally cannot solve.
> Regardless of how well your GC works, you will never prevent memory leaks
> all the time.


Jude Nelson mentioned that he disliked GC for *systems
programming*. Makes me wonder, as a lot of system
programming is done in shell.

Most programming I've done is with GC dynamic languages.
That I'm ignorant of a lot of details of memory allocation
hasn't been a big obstacle up to now... although I confess
all my work is at the applications level.

> At this point, you would nod and say "yes, but so what - half
> a loaf is better than none". So, GC does not solve the problem, and it
> doesn't make it worse. Or does it? At least some of the time you are
> required to make certain that resources are released manually. If the
> documentation is spotty - for example, the majority of opensource have poor
> documentation - how are you supposed to know which resources require release
> and which are collected? In most languages if you override the collector to
> make sure, you can get questionable results. All of this leads back to
> something bad: unreliable code.
>
> The truth is pretty hard to ignore when non-GC languages have more use
> scenarios that GC ones. Not only does GC not solve the problem, it makes
> the language more complex. Its real-world use and reliability is actually
> diminished. What is the point?
>
>
> > I think that's the right approach. It simply isn't an all-or-nothing
> matter.
>
> I would respectfully disagree. I think language design would be better
> served by instead of trying use GC, that the compiler flagged any code that
> allocates but does not release resources as an error. The goal is to make
> more reliable code, not to muddy the water with code that works most of the
> time.
>
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--
Joel Roth