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Re: [squeak-dev] Falsehoods programmers believe about Smalltalk

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Richard O'Keefe

Re: [squeak-dev] Falsehoods programmers believe about Smalltalk

I have my own Smalltalk system implemented as a batch compiler via C.

This was originally just going to be a baseline for a student wanting

to work on JIT, but he went elsewhere and I found the system surprisingly

useful.  I also wanted something that hewed closely to the ANSI Smalltalk

standard, but could diverge in other matters (like not having dynamic code

modification).

- All Smalltalk bytecode sets are stack-based VM. (?)

My system has no bytecodes.  Smalltalk=>C=>native code.

- Bytecodes are always fixed-size. (?)

False back in the Blue Book.  Why does it matter anyway?

- Most of the time spent by a VM is in the instruction interpreter. (actually it's in the GC right?)

There is no interpreter in my system, and many modern systems use a JIT.

That or they generate Javascript or JVM instructions or .NET or something,

and then _that_ gets turned into native code.

- You cannot serialize objects containing blocks. (IIRC one can use MessageSends)

True in my system but that's because blocks contain pointers to native code and may

contain pointers into the C stack. I have plans to work around this, but it has not been

a priority. Something I don't ever plan to deal with is objects containing references to

external objects (memory-mapped segments, file descriptors, sockets, ...) and it is not

at all clear to me what the semantics should be.

BinaryObjectStorage in VisualWorks has no trouble with blocks.

I meant to try this in Pharo 7.0. The image I just installed via the launcher has

no DataStream, ReferenceStream, or SmartRefStream, but the class comment

for MCDataStream begins

"This is the save-to-disk facility.

A DataStream can store one or more objects in a persistent form.

To handle objects with sharing and cycles, you must use a ReferenceStream

instead of a DataStream. (Or SmartRefStream.) ReferenceStream is typically

faster and produces smaller files because it doesn't repeatedly write the same Symbols."

This was also the case back to Pharo 2.0. What *is* the persistence scheme in Pharo these days?

- Image cannot be bootstrapped. (This is possible in ST/X and now in Pharo I think).

There are no images in my system.

- All Smalltalks includes UI classes. (GemStone doesn't have AFAIK).

It depends on what you mean by "include". Gnu Smalltalk *has* UI classes but they

are not loaded by default.

- All implementations uses direct pointers, (GST?)

True in my case, but that's because I'm lazy and using the Boehm collector.

- All implementations uses green threads. (VAST? MT?)

False in my case. A Process is a POSIX (red) thread and no green threads exist.

This meant having to keep the interface fairly lean, but honestly wasn't that hard,

since the Boehm collector handled the hard stuff.

On Tue, 22 Jan 2019 at 13:27, Hernán Morales Durand <[hidden email]> wrote:

Done.

I have some possible myths, but I'd like to confirm or reject:

- All Smalltalk bytecode sets are stack-based VM. (?)
- Bytecodes are always fixed-size. (?)
- Most of the time spent by a VM is in the instruction interpreter. (actually it's in the GC right?)
- You cannot serialize objects containing blocks. (IIRC one can use MessageSends)
- Image cannot be bootstrapped. (This is possible in ST/X and now in Pharo I think).
- All Smalltalks includes UI classes. (GemStone doesn't have AFAIK).
- All implementations uses direct pointers, (GST?)
- All implementations uses green threads. (VAST? MT?)

I'm sure people in this list will have a lot more myths heard from Conferences, Forums, Videos, Talks, etc. Like the guy who said Smalltalk was dead. So if you did something which could be ignored publicly, please don't hesitate to reply or ping me to get added as collaborator.

Cheers,

Hernán

El dom., 20 ene. 2019 a las 22:41, Eliot Miranda (<[hidden email]>) escribió:
Hi Hernán,

On Sun, Jan 20, 2019 at 2:31 PM Hernán Morales Durand <[hidden email]> wrote:
Hi there,

I just created a GitHub repo to collect myths around Smalltalk-based technologies: Pharo, Squeak, VW, VAST, Smalltalk/X, GNU/ST, etc. in the spirit of the Falsehoods lists [1-4].

This is just a draft now but please feel free to add falsehoods based on your own experiences. Examples are greatly appreciated.

You want pull requests? If not, would you give me write permission? I'd love to add to the "Smalltalk is obsolete" section...

https://github.com/hernanmd/falsehoods_smalltalk

Cheers,

Hernán

[1] https://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time
[2] https://chiselapp.com/user/ttmrichter/repository/gng/doc/trunk/output/falsehoods.html
[3] https://github.com/googlei18n/libphonenumber/blob/master/FALSEHOODS.md
[4] https://meta-package-manager.readthedocs.io/en/develop/falsehoods.html

--
_,,,^..^,,,_
best, Eliot

Sven Van Caekenberghe-2

Re: Falsehoods programmers believe about Smalltalk

> On 27 Jan 2019, at 03:38, Richard O'Keefe <[hidden email]> wrote:
>
> What *is* the persistence scheme in Pharo these days?

FUEL is the standard binary serialiser (which can do blocks, execution stacks, etc).
STON is the standard textual serialiser (that cannot do blocks).

It has been like that for many versions.