9984 2016-07-20 09:21:07 +0000 Suggested clarification of the '3.1.2. Variable Expansion' section 2016-08-01 22:32:52 +0000 1 1 9 Documentation BitBake User Manual bitbake-manual 2.2 x86 Multiple RESOLVED FIXED 01 August 2016: RESOLVED Medium enhancement 2.2 M3 1 ulfalizer srifenbark bluelightning sgw srifenbark --- --- Done (doc changes complete) oldest_to_newest 64212 0 ulfalizer 2016-07-20 09:21:07 +0000 Hello Scott, I've seen people being confused about the behavior of '=' when variables in the right-hand side are changed after the assignment. Rewriting/expanding '3.1.2. Variable Expansion' as follows might help: 3.1.2. Variable expansion Variables can reference the contents of other variables using a syntax that is similar to variable expansion in Bourne shells. The following assignments result in A containing "aval" and B evaluating to "preavalpost". A = "aval" B = "pre${A}post" Note { Unlike in Bourne shells, the curly braces are mandatory: Only ${FOO} and not $FOO is recognized as an expansion of FOO. } The '=' operator does not immediately expand variable references in the right-hand side. Instead, expansion is deferred until the variable assigned to is actually used. The result depends on the current values of the referenced variables. The example below should clarify this behavior: A = "${B} baz" B = "${C} bar" C = "foo" *At this point, ${A} equals "foo bar baz" C = "qux" *At this point, ${A} equals "qux bar baz" B = "norf" *At this point, ${A} equals "norf baz" Contrast this behavior with the ':=' (immediate variable expansion) operator, which is described below. 64213 1 ulfalizer 2016-07-20 09:24:38 +0000 Hmm... was supposed to be *'s at the end too: A = "${B} baz" B = "${C} bar" C = "foo" *At this point, ${A} equals "foo bar baz"* C = "qux" *At this point, ${A} equals "qux bar baz"* B = "norf" *At this point, ${A} equals "norf baz"* 64279 2 srifenbark 2016-07-21 16:53:26 +0000 Ulf, Here is the new section - http://www.yoctoproject.org/docs/2.2/bitbake-user-manual/bitbake-user-manual.html#variable-expansion. Thanks, Scott 64280 3 ulfalizer 2016-07-21 16:57:48 +0000 Looks good. Thanks, Ulf 64281 4 ulfalizer 2016-07-21 17:30:54 +0000 Thought of one more thing that might be nice to add to the end of 3.1.11. Inline Python Variable Expansion: Note { Inline Python expressions work just like variable expansions insofar as the '=' and ':=' operators are concerned. Given the following assignment, <code>foo()</code> will be called each time FOO is expanded: FOO = "${@foo()}" Contrast this with the following immediate assignment, where <code>foo()</code> is only called once, while the assignment is parsed: FOO := "${@foo()}" } 64283 5 srifenbark 2016-07-21 18:05:16 +0000 Here is the new note: http://www.yoctoproject.org/docs/2.2/bitbake-user-manual/bitbake-user-manual.html#inline-python-variable-expansion Thanks, Scott 64288 6 ulfalizer 2016-07-21 18:12:15 +0000 Looks good to me. Thanks, Ulf 64290 7 srifenbark 2016-07-21 18:17:44 +0000 Ulf, Closing the bug out. thanks, Scott 64755 8 ulfalizer 2016-08-01 21:54:43 +0000 Hello, I noticed that this change (and maybe others too) disappeared from the BitBake User Manual. Was that an error? Cheers, Ulf 64756 9 ulfalizer 2016-08-01 21:56:08 +0000 (In reply to comment #8) > Hello, > > I noticed that this change (and maybe others too) disappeared from the > BitBake User Manual. Was that an error? > > Cheers, > Ulf At least 9985 disappeared as well. 64758 10 srifenbark 2016-08-01 22:23:40 +0000 Ulf, Ok - I was trying to sync up my working repo with the actual upstream bitbake repo, which holds the docs. In doing so, I did a "git pull" and apparently the changes I had made have not been merged into the actual upstream yet (they will be as Richard Purdie gets to these but not always right away). I rebuilt the manual from my poky-contrib/srifenbark/bb-manual area and the changes are there... they are not lost. Just not merged yet. You can check those links out again to verify. Sorry. Scott 64760 11 ulfalizer 2016-08-01 22:27:48 +0000 (In reply to comment #10) > Ulf, > > Ok - I was trying to sync up my working repo with the actual upstream > bitbake repo, which holds the docs. In doing so, I did a "git pull" and > apparently the changes I had made have not been merged into the actual > upstream yet (they will be as Richard Purdie gets to these but not always > right away). > > I rebuilt the manual from my poky-contrib/srifenbark/bb-manual area and the > changes are there... they are not lost. Just not merged yet. > > You can check those links out again to verify. > > Sorry. > > Scott OK, no worries. Just wanted to make sure they hadn't been accidentally deleted. Might've lead to a PITA later. :) Cheers, Ulf 64763 12 srifenbark 2016-08-01 22:32:52 +0000 Ha - yes, it could have.