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Concurrent stackframes execution and matching

 When you want to integrate two clean pieces of code together people often write glue code, subclasses or change the interfaces to combine the behaviours together. There's a better way. Imagine you have a security manager, transaction manager and a locking manager and a btree. How do you combine them together without creating a mess of the interfaces? What if you could have concurrent stackframes for each library under integration for each piece of code for each function call and match stacktraces to behaviour . In other words, I specify the stackframe that matches where I want do do something and the compiler automatically weaves the code into the right place. You would need parallel return values.
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I often write reference implementation APIs.

For example, I wrote a btree, SQL parser, executor and I wrote multiversion concurrency control implementation.

Then I want to glue them together and this is where it becomes messy. The complexity rachets upwards when you combine these systems together Independently they are simple and have clear APIs.

You don't want to change the reference API as they're perfect how it is but if you have another requirement you do not have much choice in passing around extra context or changing the signature or using composition

I want to hide this mess and move it to the compiler.

Print out two stacktraces of two different pieces of code and then Merge them together in an arbitrary order by weaving the points that each separate method is running in. And having access to the surrounding context that a method is executing in. That's this idea.

I kind of want access to the parameters of a function of the code I am integrating against, and maybe local variables.

I cannot change the invariants of the function being matched against though and I don't want to change that code or its interfaces.

So what can we match against? The stackframe! This would work for an interpreted language but for a compiled language it's a job for the compiler.

The stackframe represents the execution at this point in time of the function being executed. And local variables and branches.

I should be capable of weaving in calls to each and between my reference implementations with some glue code that specifies the matching parameters of the method signature of intermediary stacktraces of any of the reference implementation code.

The ultimate matching syntax needs to be tolerant of signature changes of the underlying reference implementations.

All security managers have a function that decides if you can do something. You want to weave this into the btree ln code.

Essentially you have two execution environments executing different code in lockstep and have access to each others signature and local variables.

The stackframe of a function changes as local variables are changed.

I think the most similar example of this idea is aspect oriented programming but I think I take a different approach

Every if statement is a branch. If I want to target a particular branch of another piece of code I need some way of labelling the branch. We don't often label our branches.

—chronological, May 16 2022

She no easy https://stackoverfl...chitecture-on-linux
[4and20, May 16 2022]

Client side decorators https://en.m.wikipe...20the%20X%20server.
Client side decorators were historically part of window managers [chronological, May 16 2022]

Server side decorations on wayland https://blog.martin...ations-and-wayland/
Read the comments [chronological, May 16 2022]

Parallel processing https://www.dais.un.../4_SharedMemory.pdf
now with extra Italians [4and20, May 16 2022]

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       SO many words I don't know. Cool. (+)   

       I'm just going to sit this one out, hang around and learn from the responses if that's okay.   

       This is a hairy beast. If it can't be done with a *nix stackframe, someone has considered or discounted it.   

       // Essentially you have two execution environments executing different code in lockstep and have access to each others signature and local variables. //   

       I have argued that objects or variables should have changeable states which are tracked by a central processor. In this way you might be able to simply assign a number or property to (new) objects without using loops at all. The only loops would be in the central processor.
—4and20, May 16 2022
   

       What do you mean by "combine the behaviours together"?
—pertinax, May 16 2022
   

       So my lock manager does some thing with locks and my btree does something with leaf and internal nodes.   

       When there is a split in the btree I need to do something in the lock manager and vice versa.   

       It leads to a mess of code of mixed responsibilities.   

       The trend of software engineering is single responsibility pattern but at some point you need to be responsible for two things to integrate them.   

       So I specify a third place and coordinate the two things without changing the underlying code of the pure things.   

       It's like if you have a window manager and a kernel and a desktop environment. Where do you put functionality such as cut and paste.
—chronological, May 16 2022
   

       See the debate regarding window decorations in Linux. It's a mess nobody wants to integrate the work.
—chronological, May 16 2022
   

       I should add this is a job for the compiler.
—chronological, May 16 2022
   

       Suppose you have a btree class, a SQL Parser class and a currency-set class, as in your first example.   

       Suppose you have a use case where they will all have to work together.   

       My first thought is, what is wrong with having a MyUseCaseHandler class, which owns an instance of Btree, an instance of SqlParser and an instance of CurrencySet, and farms out most of its work to those objects?   

       Then I see your example about wanting to do something in a lock-manager every time there's a split in a btree, and I'm assuming here that a split in a Btree is an internal operation, that would not be triggered explicitly from an API.   

       All right; surely you still have a fairly simple MyUseCaseHandler class, and you add an optional callback in your Btree class and then, when you initialise the Btree belonging to your MyUseCaseHandler, you pass it a callback function which calls the API on your lock-manager (or whatever the other class is).   

       Why does that approach not work? Would the provision of the callback hook count as a change to the reference API?
—pertinax, May 16 2022
   

       Yes, I think I see. Some compilers might have methods to keep variables in the stack or register longer.   

       Generally speaking, it seems to me that [pertinax] is describing some much preferable serial approach. Would a compiler even let you specify parallel processing?   

       The [link] describes basic parallel processing, using Linux pthreads, whatever that means. You are thereby inviting hellspawn to eat your brain and memory.
—4and20, May 16 2022
   

       Of all of chronological's entries, I understand this one the least, but it likely makes the most sense. I think we've found an area where he actually knows what he's talking about, or can at least baffle me with bullshit.
—RayfordSteele, May 16 2022
   

       Pertinax, I agree with your approach, I too favour composition over inheritance. But I try use the tell Don't ask pattern.   

       As for callbacks, the JavaScript world kind of rejects them for promises. And there are a number of pipeline libraries for async programming.   

       You've understood the problem.   

       I am thinking of the scenario when you don't have authority over the entire codebase but one small part. You don't have authority to modify the code of some library you're using, you are at the mercy of the library author to provide callbacks or hooks to enable you to extend the library with behaviour you want.   

       It's a SOLID principle that classes should be closed to modification but open to extension.   

       I think how we extend classes or software is painful so that's why I created this idea.   

       When I used the word parallel I do not mean threading or using multiple cores on the CPU but the stackframes of your glue code being sequentially executed in lockstep with your glue code to "drive" out the coordination of different pieces of the system.   

       Print out two stacktraces of two different pieces of code and then Merge them together in an arbitrary order by weaving the points that each separate method is running in. And having access to the surrounding context that a method is executing in. That's this idea.   

       If someone asked me to write an extension to IntelliJ or Postgresql I think I would be not amused as these are extremely sophisticated pieces of software. Extending them would require you be intimately familiar with each of the codebases. They are mature pieces of software with mature extension frameworks. But very complicated. It's not something you can do without a heavy investment in time.   

       I want to be capable of reading any class of a piece of software and essentially extending it with knowledge of that classes innermost workings which is a violation of SOLID but it would mean extending other people's work would be easier. It would break on the next release though as everything is moved around.   

       Usually you know what data you need to glue together and when to glue it together. This idea solves that problem. Essentially you are executing two separate callstacks stack traces simultaneously but as if it's one single function. It's as if all the code I am running is a single function and I'm deciding what to place "around" "before" other code.   

       Usually you end up needing to pass extra parameters and you change the interface of the code and that causes breakage.   

       To clarify the glue code would look like pattern matching syntax on methods, classes and references to parts of code in libraries and other classes. Kind of like a patch.
—chronological, May 16 2022
   

       I should add that async/await functionality in many programming languages including JavaScript and Rust is implemented as a state machine. So the weaving of methods is doable.
—chronological, May 16 2022
   

       I have one clean flow of execution from top to bottom in this part of the system and another clean flow of execution from top to bottom over here.   

       How can I pause execution deliberately halfway through a method and execute this method in the context of the original method.   

       Without changing the underlying sourcecode.
—chronological, May 16 2022
   

       I should probably use the word concurrent and not parallel as they wouldn't be executed in parallel but they would be concurrent.
—chronological, May 16 2022
   

       //It would break on the next release//   

       {Peers at [chronological] over the top of spectacles}   

       {Steeples fingers}   

       ...   

       {Raises eyebrows}
—pertinax, May 16 2022
   

       //How can I pause execution deliberately halfway through a method and execute this method in the context of the original method.//   

       By using a scripting language?
—Voice, May 16 2022
   


 

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