Smalltalk - Re: MethodFinder.Blocks

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Re: MethodFinder.Blocks

Posted by Eliot Miranda-2 on Oct 17, 2019; 6:47pm
URL: https://forum.world.st/MethodFinder-Blocks-tp5105421p5105627.html

On Thu, Oct 17, 2019 at 11:13 AM Eliot Miranda <[hidden email]> wrote:

On Wed, Oct 16, 2019 at 2:55 AM Thiede, Christoph <[hidden email]> wrote:

Hi Marcel,

as I see it, this Blocks check only restricts the possible hits, so removing it should not damage any existing functionality. (I am *not* talking about modifying Dangerous!)

And if you do

MethodFinder methodFor: {{#(1 2). [:x | Smalltalk saveSession. false]}.#()} "pls don't run this!"

you will surely expect the side effects to be executed?

If MethodFinder were implemented using simulation (a la Context class>>runSimulated:) then we could implement a proper sandbox and completely discard Dangerous. We could catch any attempt to change the class hierarchy, save a snapshot, etc.

It would be a great project to create a subclass of Context, say SandboxContext, and have this ensure that when simulating it only creates more SandboxContexts, never a normal Context, and have SandboxContext override primitive invocation. This could be a place to intercept modification of the class hierarchy (at:put: & become: on MethodDictionary, and Array to see if an attempt is being made to assign to or become: a MethodDictionary and/or a subclasses Array). Perhaps SandboxContext would need SandboxClosure, perhaps it could simply intercept value: et al on Closure (see Context>>#doPrimitive:method:receiver:args:).

My gut tells me that while this implementation is clever, it will also be more general and more easily maintainable than the current one. There are issues; a time limit would have to be placed upon simulated executions (that's also a potential issue for the current implementation). But it would be safer since instead of relying on Dangerous to identify dangerous code it would depend on a reasonably well-defined notion of sandbox, what is possible to evaluate when searching, and what is not. One could, for example, implement an instantiation budget in SandboxContext>>#doPrimitive:method:receiver:args:.

> Just curious: what would be the block example for these examples?

MethodFinder methodFor: {{#(1 2). #even}. #(1)}. '(data1 reject: data2) '

MethodFinder methodFor: {{#(1 2). #yourself descending}. #(2 1)}. '(data1 sorted: data2) (data1 sort: data2) '

Hey, maybe we should make a small game of it? :-) GuessTheSelectorGame :D

Christoph

Von: Squeak-dev <[hidden email]> im Auftrag von Taeumel, Marcel
Gesendet: Mittwoch, 16. Oktober 2019 10:54 Uhr
An: gettimothy via Squeak-dev; [hidden email]
Betreff: Re: [squeak-dev] MethodFinder.Blocks

Hi, Christoph.

The method finder (or selector browser) has a hard-coded list of possible results (or messages) to not trigger dangerous side effects. Any new feature, such as that "quasi higher-order-message" symbol , would have to be added. Sure. But keep compatiblility with block arguments. :-)

Just curious: what would be the block example for these examples?

MethodFinder methodFor: {{#(1 2). #even}. #(1)}

MethodFinder methodFor: {{#(1 2). #yourself descending}. #(2 1)}.

Especially the latter seems kind of cryptic to me.

Best,

Marcel

Am 14.10.2019 01:27:12 schrieb Thiede, Christoph <[hidden email]>:

Hi all,

I just got irritated as I evaluated

MethodFinder methodFor: {{#(1 2). #even}. #(1)}

and got no hit.

This is because the MethodFinder stores an extra list of selector parameters that are assumed to require a block argument (Blocks) -- but nowadays this requirement is not given, as you can pass a Symbol, MessageSend, SortFunction or whatsoever, thanks to polymorphy. So (how) is this block check still relevant? If I remove it, I get the right hit and can do thinks like

MethodFinder methodFor: {{#(1 2). #yourself descending}. #(2 1)}.

Also, #ifError: will prevent any error thrown if the block does not match the selector.

Looking forward to your answers :)

Christoph

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

_,,,^..^,,,_

best, Eliot