Re: [Buildroot] [PATCH] package: fix builds with $(PKG)_FLAT_STACKSIZE

Hi Thomas,

Thank you for taking the time to review my patch!

On Thu, Aug 20, 2026 at 09:20:00PM +0200, Thomas Petazzoni wrote:
> Thanks a lot for your patch, well spotted!
>
> One thing that was missing from your commit message is the indication
> of which commit broke this, so I added that and applied your commit to
> our master branch.
>
> This feature is not actually used by any package in Buildroot, which
> explains why this problem remained unnoticed. Would you be willing to
> work on adding a simple test case in support/testing/ for this? I
> guess it could be a very simple br2-external, with a very simple
> package that uses <pkg>_FLAT_STACKSIZE.

Sure. I would be glad to add a test case for this, and I will send it as
a separate patch.

>
> Aside from that, no many of our users use Buildroot for noMMU
> platforms. Would you mind sharing your use case? Which platform are
> you using, in which context, how did you end up running into this
> <pkg>_FLAT_STACKSIZE issue?

I am working on a fork of Buildroot for HPMicro MCUs:
https://github.com/hpm-rs/buildroot

I have ported Linux to a new RISC-V MCU called HPM6750 from HPMicro
Semiconductor Ltd., and I am adding board support for it to Buildroot.

I ran into this problem when trying to run FFmpeg on it. Initially, it
failed with a "stack smashing detected" error. To resolve this, I
attempted to use FFMPEG_FLAT_STACKSIZE to allocate a larger FLAT stack,
which led me to discover the build failure caused by this bug.

>
> Again, thanks for your contribution!
>
> Thomas
> --
> Thomas Petazzoni, co-owner and CEO, Bootlin
> Embedded Linux and Kernel engineering and training
> https://bootlin.com
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