9985 2016-07-20 11:14:51 +0000 Suggested clarification and motivation for the override-style operators 2016-08-01 22:31:27 +0000 1 1 9 Documentation BitBake User Manual bitbake-manual 2.2 x86 Multiple RESOLVED FIXED 01 August 2016: IN PROGRESS REVIEW Medium normal 2.2 M3 1 ulfalizer srifenbark bluelightning sgw srifenbark --- --- Done (doc changes complete) oldest_to_newest 64214 0 ulfalizer 2016-07-20 11:14:51 +0000 Hello, I suspect the override-style operators (_append, _prepend, _remove) would be much easier to understand if some motivation was given. The existing descriptions are also vague in places. I suggest the following changes: Add to the end of '3.1.9. Removal (Override Style Syntax)': Like _append and _prepend, _remove is deferred until after parsing completes. Add a new section '3.1.10 Motivation behind the override-style operations': An advantage of the override-style operations _append, _prepend, and _remove (compared to e.g. += and =+) is that they provide "guaranteed" operations. For example, consider a class foo.bbclass that needs to add the value "val" to the variable FOO, and a recipe that uses foo.bbclass as follows: inherit foo FOO = "initial" If foo.bbclass uses the '+=' operator, as follows, then the final value of FOO will be "initial", which is not what we want: FOO += "val" If on the other hand foo.bbclass uses the _append operator, as follows, then the final value of FOO will be "initial val", as intended: FOO_append = " val" Note { It is never necessary to use += together with _append. The following sequence of assignments will append "barbaz" to FOO: FOO_append = "bar" FOO_append = "baz" The only effect of changing the second assignment to FOO_append += "baz" is to add a space before "baz" in the appended value (due to how the += operator works). } Another advantage of the override-style operations is that they can be combined with other overrides, as described in [3.2. Conditional Syntax (Overrides)]. In '3.2.3. Examples', change OVERRIDES = "foo" A = "Y" A_foo_append = "Z" A_foo_append += "X" to OVERRIDES = "foo" A = "Y" A_foo_append = "Z" A_foo_append = "X" and change ...leaving the variable set to "Z X" to ...leaving the variable set to "ZX" This avoids tricking people into thinking += is necessary when using _append. I tested it out to make sure it was correct. Cheers, Ulf 64282 1 srifenbark 2016-07-21 17:57:29 +0000 Ulf, Here is the change for 3.1.9 - http://www.yoctoproject.org/docs/2.2/bitbake-user-manual/bitbake-user-manual.html#removing-override-style-syntax Here is the new 3.1.10 section - http://www.yoctoproject.org/docs/2.2/bitbake-user-manual/bitbake-user-manual.html#override-style-operation-advantages Here is the 3.2.3 change - http://www.yoctoproject.org/docs/2.2/bitbake-user-manual/bitbake-user-manual.html#variable-interaction-worked-examples. thanks, Scott 64287 2 ulfalizer 2016-07-21 18:10:54 +0000 A few nits, otherwise fine: - "...changing the second assignment in the previous example..." would be clearer as "...changing the second assignment in the previous example to use ':='..." - There's an ending parenthesis missing in "(due to how the '+=' operator works." - The following also needs to say "ZX" rather than "Z X". I missed that when I first went through it: Finally, applying the override for "foo" results in the conditional variable A becoming "Z X" (i.e. A is replaced with A_foo). Thanks 64291 3 srifenbark 2016-07-21 18:26:27 +0000 Here are the changes: * http://www.yoctoproject.org/docs/2.2/bitbake-user-manual/bitbake-user-manual.html#override-style-operation-advantages * http://www.yoctoproject.org/docs/2.2/bitbake-user-manual/bitbake-user-manual.html#variable-interaction-worked-examples I wondered about the second one. I almost went ahead and changed it but figured if it was wrong you would catch it. Scott 64292 4 ulfalizer 2016-07-21 18:29:30 +0000 You put too much trust in me. ;) Looks good to me now. Thanks. 64293 5 srifenbark 2016-07-21 18:31:01 +0000 Thanks - closing out. 64703 6 ulfalizer 2016-07-30 20:11:21 +0000 Ops... I made a typo: ...example to use ":=" would be to add... should be ...example to use "+=" would be to add... 64741 7 srifenbark 2016-08-01 18:56:39 +0000 Ulf, See the note in http://www.yoctoproject.org/docs/2.2/bitbake-user-manual/bitbake-user-manual.html#override-style-operation-advantages for the fix. I should have realized that had to change as well. Scott 64757 8 ulfalizer 2016-08-01 22:02:11 +0000 Hello, As mentioned in bug 9984, the changes for this bug disappeared. Other changes besides 9984 and 9985 might be affected too. Cheers, Ulf 64759 9 srifenbark 2016-08-01 22:25:07 +0000 Check the link again for the change... Same explanation as the Bug 9984. Scott 64761 10 ulfalizer 2016-08-01 22:28:51 +0000 Looks good now! Thanks, Ulf 64762 11 srifenbark 2016-08-01 22:31:27 +0000 Cool - setting doc flag to "done"