Hi Robert,

On Tue, Mar 09, 2021 at 09:39:14AM -0500, Robert P. J. Day wrote:
> 
>   bitbake manual, chapter 3, examples of conditional syntax:
> 
> https://docs.yoctoproject.org/bitbake/bitbake-user-manual/bitbake-user-manual-metadata.html#examples
> 
> correctly distinguishes between A_foo_append and A_append_foo, but how
> often would one use that first form, anyway?
> 
>   most uses of conditional appending are either just straight
> appending:
> 
>   VAR_append = "fubar"
> 
> or used with an override thusly:
> 
>   VAR_append_x86 = "snafu"
> 
> is there an actual practical usage of, say:
> 
>   VAR_x86_append = "huh"
> 
> i can't remember the last time i saw something of that form and,
> while it might be worth explaining, it seems that the reader might be
> warned that that form is almost certainly *not* what they want.
> 

Yes, in 99% of the cases, you want VAR_append_foo and not VAR_foo_append.

VAR_foo_append makes sense when you want to append to VAR_foo which is a
way to override completely VAR for builds matching the foo override.
This happens in kernel-yocto recipes where branches and defconfigs are
different per machine for example.

The sneaky thing about VAR_foo_append is that it creates VAR_foo even if
it didn't exist beforehand, meaning you though you *appended* something
to VAR while you actually replaced VAR entirely with what VAR_foo_append
is set too.

Quentin
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