[PATCH 01/10] build: Generate build hash

[Chris Johns]

On 25/2/21 12:57 am, Sebastian Huber wrote:
> Update #4265.
> ---
>  wscript | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/wscript b/wscript
> index 6626fafb74..83c7c446bb 100755
> --- a/wscript
> +++ b/wscript
> @@ -1359,6 +1359,30 @@ def get_compiler(conf, cp, variant):
>      return value
>  
>  
> +def _generate_build_hash(conf):
> +    import hashlib
> +    import base64
> +
> +    build_hash = ""
> +    for key in sorted(conf.env):
> +        build_hash = build_hash + key + str(conf.env[key])

I am pleased to see the environment is being addressed but on some modern
operating systems the environment has become a bit of a beast. This means
comparable values will be near impossible if the whole environment is included
in the build hash.

Should we look to use a list that is contained? A list that effects the code on
the target? In a purest sense a hash created from the CU pieces in all target
libraries would be ideal however this is recursive.

Any chance of a build label set in the config.ini? :)

> +    for discard in [
> +        conf.env.PREFIX,
> +        conf.bldnode.make_node(conf.env.VARIANT).abspath(),
> +        conf.path.abspath(),
> +    ]:
> +        build_hash = build_hash.replace(discard, "")

I do not follow this piece of logic.

> +    state = hashlib.sha256()
> +    state.update(build_hash.encode("utf-8"))

Why the `utf-8` encode and then decode later?

> +    conf.define(
> +        "RTEMS_BUILD_HASH",
> +        base64.urlsafe_b64encode(state.digest()).decode("utf-8"),

Thank you for base64 encoding the result.

Chris