Hi.
I hope you are fine and the same for your family and friends.
In July, a proposal to add a new shell for U-Boot was posted on the mailing list [1]. The community discussed a lot about this changes, some people did not agree with it because the new shell is not compatible with the actual one (hush) [2]. So, a proposal to update U-Boot actual hush to follow what they currently have in Busybox was made [3].
Porting 2021 Busybox hush to U-Boot seems, for me, to be a good idea as we would benefit from Busybox bug fixes as well as being compatible with actual hush (in theory). We could also add new features to U-Boot hush, like functions, as they were added to Busybox.
Nonetheless, the idea of this port is to be compatible. In practice, I noted some cases when this is actually not the case. The first one can be related to how && and || operators were handled in hush. So, the following: false && false || true Returns 0 on Busybox 2021 hush and 1 on U-Boot. The behavior of 2021 is coherent with the definition of these operators [4]:
The return status of AND and OR lists is the exit status of the last command executed in the list.
An other example concerns variable expansion, where foo='bar "quux" is expanded to bar quux in U-Boot and bar "quux in Busybox.
I do not have a real opinion on the second one, as I think local variable set in U-Boot scripts are quite simple as people do not try to do: foo="bar "quux 'quuz' """corge". The first one is maybe more problematic. Grepping "if test" shows me that the more complex if condition seems to be under the form: if first_test_ AND/OR second_test Here also, people seems to no try to write complex expression like: foo || bar; echo quux && quuz.
So, porting Busybox 2021 hush can solve bugs we have currently in U-Boot, but what if fixing these bugs lead to a board script failing and so a device not booting... I would like to have the opinion of the community on this question.
Best regards.
--- [1] https://lists.denx.de/pipermail/u-boot/2021-July/453347.html [2] https://lists.denx.de/pipermail/u-boot/2021-July/453790.html [3] https://lists.denx.de/pipermail/u-boot/2021-July/453848.html [4] https://linux.die.net/man/1/bash