D vs VM-based platforms

[Brad Roberts]

Benji Smith wrote:
> Walter Bright wrote:
>> I just don't get the reason for a VM. It seems like a solution looking 
>> for a problem.
> 
> Some of the benefits of using a VM platform:
> 
> 1) Dynamic classloading. Linking is greatly simplified, and my code 
> doesn't need to be written differently depending on whether I'm linking 
> dynamically or statically.
> 
> 2) Better tools for profiling, debugging, reflection, and runtime 
> instrumentation than are typically available for natively-compiled 
> languages.
> 
> 3) Better memory management: with the memory manager located in the VM, 
> rather than in the application code, the collection of garbage is much 
> more well-defined. Since all classes are loaded into the same VM 
> instance, there's only a single heap. Consequently, there's never an 
> issue of what happens when an object passes from one module to another 
> (as can be the case when a native library passes an object into the main 
> application, or vice versa).
> 
> 4) Better security/sandboxing. If you write a pluggable application in 
> C++, how will you restrict plugin authors from monkeying with your 
> application data structures? In the JVM or the CLR, the VM provides 
> security mechanisms to restrict the functionality of sandboxed code. A 
> particular CLR assembly might, for example, be restricted from accessing 
> the file system or the network connection. You can't do that with native 
> code.
> 
> Sure, it's possible for natively-compiled languages to offer most of the 
> same bells and whistles as dynamic languages or VM-based platforms. But, 
> in the real world, those abstractions are usually difficult to implement 
> in native code, so they become available much more readily in virtual 
> machine.
> 
> --benji

Interesting.  Paraphrasing your reply:  These are benefits of VM's, but 
no they're not.

They're above list of 'benefits' are some things that current VM 
implementations and the languages that sit on top of them and the 
provided libraries that sit on top of them all add up to provide. 
They're very much not attributes of the VM underneath nor of VM's in 
general.

Please be careful when attributing causal effects.  A favorite phrase: 
correlation is not causation.

Later,
Brad