BB explanation of BB_ENV_PASSTHROUGH is confusing

BB explanation of BB_ENV_PASSTHROUGH is confusing

[Robert P. J. Day]

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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 BitBakeοΏ½s 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?

rday

Re: [docs] BB explanation of BB_ENV_PASSTHROUGH is confusing

[Richard Purdie]

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

Re: [docs] BB explanation of BB_ENV_PASSTHROUGH is confusing

[Quentin Schulz]

Hi Richard, Robert,

On 1/7/26 3:46 PM, Richard Purdie via lists.yoctoproject.org wrote:
> 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
> 

See 
https://lore.kernel.org/yocto-docs/20260114-env-passthru-v1-1-fd5ef76eab61@cherry.de/

Cheers,
Quentin