Cross-compiling a flatpak

[Valentin David]

It is possible to do that using buildstream. Import native SDK to /,
target SDK to your sysroot, build cross-compiling binutils and gcc.
Then you can build your application. You just need to export it with
"flatpak build-export".

On Thu, Mar 22, 2018 at 5:17 PM, Corentin Noël
<corentin.noel at collabora.com> wrote:
> Hi everyone,
>
> I'm playing a little bit with flatpak and wanted to experiment cross-
> compilation with it.
> I haven't seen anything regarding cross-compilation right now, but I'm
> wanting to further investigate this issue.
>
> I wanted to know if you had some thoughts about it, or if there was
> some plans documented somewhere (or in someone's mind)
>
> Here are my thoughts when I look at this issue:
>
> Let's imagine that I'm using a x86_64 system and want to build a
> `bar.foo.HelloWorld` application targetting the aarch64 architecture.
>  * my application will target the `org.freedesktop.Platform//1.6`
> runtime and require the `org.freedesktop.Sdk//1.6` sdk
>  * I start a build with `flatpak build` using a new --target=aarch64
> flag showing my intention to cross-build
>    * `org.freedesktop.Sdk/x86_64/1.6` and
> `org.freedesktop.Platform/x86_64/1.6` are mounted as usual to start the
> compilation.
>    * the target flag makes flatpak mount a
> `org.freedesktop.Sdk.Extension.Cross-aarch64/x86_64/1.6` SDK extension
> (mounted under /usr/lib/sdk/Cross-aarch64), this extension contains all
> the toolchain for building to the aarch64 architecture. (and it might
> also contain some useful things for cross-compilation like a meson
> crossfile definition)
>    * the target flag makes flatpak mount
> `org.freedesktop.Platform/aarch64/1.6` and
> `org.freedesktop.Sdk/aarch64/1.6` (and their dependencies) under
> /sysroots/aarch64/ as it is doing for the native architecture in /
>    * the build happens targetting the sysroot in /sysroots/aarch64/
>    * the resulting flatpak is define to be aarch64
>
> So with the current flatpak implementation I'm mostly missing two
> parts:
>  * Be able to mount at build time a Sdk & Runtime of a foreign
> architecture in a well-defined location
>  * Define the resulting flatpak as being of another architecture
>
> Do you think that it's the right way to do it and that it's something
> that might be implemented in flatpak?
> _______________________________________________
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-- 
Valentin David
valentin.david at gmail.com