Re: [docs] BB explanation of BB_ENV_PASSTHROUGH is confusing

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Wed, 2026-01-07 at 06:39 -0800, Robert P. J. Day via lists.yoctoproject.org wrote:
> 
> here:
> 
> https://docs.yoctoproject.org/bitbake/bitbake-user-manual/bitbake-user-manual-ref-variables.html#term-BB_ENV_PASSTHROUGH
> 
> the explanation:
> 
> "Specifies the internal list of variables to allow through from the
> external environment into BitBake’s datastore. If the value of this
> variable is not specified (which is the default), the following list
> is used: BBPATH, BB_PRESERVE_ENV, BB_ENV_PASSTHROUGH, and
> BB_ENV_PASSTHROUGH_ADDITIONS."
> 
> seems weird since it suggests that if the value of that variable is
> not specified, the list that is used recursively *includes* the
> variable itself. and this doesn't seem to match the code from
> lib/bb/utils.py, which does *not* include that variable:
> 
>   def preserved_envvars():
>     """Returns the list of variables which are taken from the environment and
>     placed in the metadata."""
>     v = [
>         'BBPATH',
>         'BB_PRESERVE_ENV',
>         'BB_ENV_PASSTHROUGH_ADDITIONS',
>     ]
>     return v + preserved_envvars_exported()
> 
> can someone clarify how that explanation should be interpreted? or how
> it might be made clearer?

It probably needs updating after this:

https://git.openembedded.org/bitbake/commit/lib/bb/utils.py?id=0a33b560233b983456178541603ab96fea22238b

Cheers,

Richard