[bitbake-devel] wanting clarification on overrides, _append, += and combinations of those

[Robert P. J. Day]

  preparing my own write-up on how bitbake processes combinations of
overrides, _append and += and ran across an example in oe-core that is
unnecessarily whitespacey, just wanted to make sure i was
understanding this properly.

  in the current bitbake user manual, there's this example of mixing
overrides, _append and +=:

  OVERRIDES = "foo"
  A_foo_append = "X"
  A_foo_append += "Y"

  This behaves as per the first case above, but the value of A would
  be "X Y" instead of just "X".

  that, of course, makes sense as the "+=" operator automatically adds
a leading space to what is being appended.  so for fun, i scanned all
of oe-core looking for examples of "_append.*+=" for classroom demo
purposes, and the *only* examples i found were in
meta/recipes-devtools/python/python-smartpm_1.4.1.bb:

RDEPENDS_python-smartpm_append = " python-smartpm-backend-rpm python-codecs python-textutils python-xml"
RDEPENDS_python-smartpm_append += " python-fcntl python-pickle python-crypt python-compression python-shell"
RDEPENDS_python-smartpm_append += " python-resource python-netclient python-threading python-unixadmin"

  i can see that that first line *does* need an explicit leading space
in the value being assigned, but the next two "+=" lines don't, do
they?  it won't hurt, of course, you'll just *two* spaces inserted
instead of one.  but i just want to make sure i understand what's
happening there since it has the potential to be confusing for someone
trying to follow along.

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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