Hi.
Le lundi 23 août 2021, 13:20:10 CEST Wolfgang Denk a écrit : > Dear Francis, > > In message <2787647.e9J7NaK4W3@pwmachine> you wrote: > > 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. > > Thanks a lot, much appreciated. > > > Nonetheless, the idea of this port is to be compatible. > > My recommendation is not to try to be bug-compatible, i. e. is the > current U-Boot version of hush behaves different than the recent > one, we should check how other POSIX compatible shells behave. > I would expect that in most cases the old hush in U-Boot has a bug, > which has been fixed in the recent version. > > In such a situation, we should accept the bug fix and not try tokeep > the old, buggy behaviour of the old version. > > > 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. > > This is a clear bug in the old version. It's good to see it fixed > in the recent code. > > > An other example concerns variable expansion, where foo='bar "quux" is > > expanded to bar quux in U-Boot and bar "quux in Busybox. > > I guess you mean foo='bar "quux' ? [ foo='bar "quux" is > missing the closing apostrophe.] Sorry, I indeed missed the closing apostrophe. > > Again, this is a bug in U-Boots command line parsing. > > > 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. > > We should port the recent version of hush without hesitating about > bug compatibility of expected use cases. We can'tknoww if peple > didn't use afeature because the ran into problems with it, or > because it's just not their programming style. > > > 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... > > The new version should be optional in any case, at least for some > longer migration period to give users time to test their scripts. > If someone selects the new version in his board configuration, he > probably has run enough tests to make sure his scripts are working > fine in the new environment. I added a choice in Kconfig to permits user to select the parser they want to use (either the old or the new one). By default, the old one is selected. More generally, I see it seems to be a consensus over going with the new 2021 behavior (which contains bug fixes compared to old one) rather than sticking with the old (and sometime buggy) behavior. Thank you a lot for all your comments! > > Best regards, > > Wolfgang Denk
