On Fri, Jul 03, 2020 at 03:31:33PM +0100, Richard Purdie wrote: > I'm growing increasingly concerned about default value assignments in > OE. The basic problem is people don't understand the way default values > work and the mechanisms we do have don't let people do all the things > they want to do. > > I'll pick on the example found by Ross/Jon in meta-arm. If you set: > > BB_HASHBASE_WHITELIST += "X" > > in layer.conf, the BB_HASHBASE_WHITELIST ?= "Y" from bitbake.conf is > lost as by then the variable already has a value. Another user reported > the same issue today in irc.
I think DISTRO_FEATURES is (or at least was) behaving the same and that's probably what more people often tend to change in local.conf than BB_HASHBASE_WHITELIST. I always recommend to just use _append in such cases and verify with "bitbake -e" when in doubt. > Whether that could/should be some new assignment operator, or whether > we could "rescue" ??= I'm also not sure. A new operator would certainly > be safer. > > Does anyone else: > > a) Agree there is a usability issue here? I agree that people struggle with it, but luckily "bitbake -e" is invaluable help to see what went wrong (and hopefully soon they will learn to use "bitbake -e" before asking on ML). People are also complaining that there are already too many operators (4 assignments, 3 for append/prepend, remove and overrides) adding another to the mix IMHO doesn't improve the overall usability. Cheers,
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