[Discuss-gnuradio] UHD / GNU Radio / Volk Compatibility with Mac OS X 10.11 "El Capitan"

[Michael Dickens]

Today (Wednesday, Sep 30), Apple released its latest OS for free
download: 10.11 "El Capitan". This new OS comes with Xcode 7.0.1, which
provides clang 7 (700.0.72) and (likely) llvm 3.7 -- both updates from
those provided in Xcode 6 or Xcode 5. With each new Xcode generation,
some APIs are deprecated and new ones are added.

With the move from Xcode 6 to 7, it looks like none of the APIs used
directly by UHD, GNU Radio, or Volk have been deprecated or even changed
at all. The same goes for the vast majority of their dependencies.

That is, with one BIG exception: Qt4. Qt 4.8.7 has officially been in
"end of life" (EOL) except for critical updates for a while now. Some of
the APIs used by it still worked with Mac OS X 10.10 even though they
were officially deprecated in 10.6. Now, some of those deprecated
interfaces have been removed in 10.11, and the Qt folks have stated that
they will not be fixing the issues in Qt4 any longer. They provide Qt5,
and the latest release should work with 10.11 (and, should also go back
to at least 10.8 if not 10.6 for compatibility). [1]

One piece of possible good news is that if one has the 10.10 software
developer kit (SDK) installed in Xcode, then that can be used for
building Qt4 & the build will still work correctly in 10.11. The bad
news is that the 10.10 SDK does not come with Xcode 7; one can only get
it by installing Xcode 6 first, then upgrading to Xcode 7. Apple
provides no good way for us to do this install that I have found, nor a
good way to get the 10.10 SDK in the first place. For many Mac OS X
users (such as myself), they will start with a clean boot drive &
install everything from scratch instead of updating. Thus, this method
is not a generally usable option.

Another possible piece of good news is that because these API issues
have been fixed in Qt5, those fixes can be backported to Qt4 with some
degree of correctness. I doubt that the backports can be made to
function as well as the original, but it's a small price to pay for
overall Qt4 functionality. Given the issues with using the 10.10 SDK,
I'm moving to this method of fixing Qt4. [2]

Thus, with the exception of all Qt functionality in GNU Radio, I have
verified that UHD, Volk, and GNU Radio otherwise work out of the box in
Mac OS X 10.11. For example, a "uhd_fft using wx" that I keep around
works flawlessly, as do all of the core tests (as well as on 10.9 or
10.10) and some other tests I perform on the side.

Not that this has to happen, but now would be a good time to push hard
in GNU Radio to move from using Qt4 to using Qt5. I could EOL Qt4 in
MacPorts and move my efforts into Qt5. I don't expect this to happen any
time soon, thus I'll spend some time seeing if backporting is viable. -
MLD

[1] https://bugreports.qt.io/browse/QTBUG-48079
[2] https://trac.macports.org/ticket/48129