RetroBBS - comp.lang.c++ - Re: Find data somewhere on the stack

Re: Find data somewhere on the stack

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Date: Tue, 18 Jul 2023 12:34:12 -0700 (PDT)
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Subject: Re: Find data somewhere on the stack
From: cauldwell.thomas@gmail.com (Frederick Virchanza Gotham)
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by: Frederick Virchanza - Tue, 18 Jul 2023 19:34 UTC

On Sunday 23 April 2023, Frederick Virchanza Gotham wrote:
>
> So if we push this UUID onto the stack,
> and then place our data right beside it on
> the stack, then later on we can search the
> stack for this UUID and we'll find our data
> right beside it.

It's taken me 3 months but today I've come up with a legitimate use for this.

If you've been following the C++ Standard Proposals mailing list these past few days, I'm trying to come up with a universal header file to ensure elision of move/copy operations with Named Return Value Optimisation.

I order to implement this on 64-bit ARM with the aarch64 instruction set, I need to write a function that will:
(1) Move address of return value into 1st parameter
(2) Jump to a location stored in a thread_local variable

It turns out that accessing thread_local variables on aarch64 isn't so simple, as there's more than one system for storing them, see how complicated it can be here:

http://bambowu.github.io/linux/RelocationAndTheadLocalStorage/

Furthermore I want the code to work fine on a microcontroller that doesn't have multithreading support.

And so instead of putting the jump address in a thread_local variable, I'll just push it onto the stack beside a known UUID.

I knew this would come in handy somewhere.

Deliver yesterday, code today, think tomorrow.

devel / comp.lang.c++ / Re: Find data somewhere on the stack

Subject	Author
Re: Find data somewhere on the stack	Frederick Virchanza Gotham