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List:       macports-dev
Subject:    Upcoming ARM-based Macs and importance of universal variant
From:       Ryan Schmidt <ryandesign () macports ! org>
Date:       2020-04-27 8:35:24
Message-ID: CDBB4BB7-6A12-477E-BBBE-029345D4FB1F () macports ! org
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Recent news reports say Apple expects to release Macs next year that =
will use ARM CPUs instead of Intel. So this will be another transitional =
time, just like the previous i386-to-x86_64 transition and the =
ppc-to-i386 transition, during which we will have a userbase where not =
everyone is using the same CPU.

The universal variant in MacPorts allows users to build a port so that =
it can run on multiple architectures. Some people use MacPorts to build =
software that they then redistribute to others (i.e. using `port mpkg` =
or `port mdmg`); by using the universal variant and the right =
universal_archs, those redistributed versions should work on any Mac =
regardless what processor it uses.

My impression is that over the past few years we've allowed our support =
for universal builds in our port collection to bitrot a bit, due to a =
number of factors: universal builds are not possible with the macOS =
10.14 SDK and later and probably most users and developers now use macOS =
10.14 or later (or 10.13 with Xcode 10, which is also affected); many =
projects have switched to the new meson build system for which IIUC we =
have not developed a universal variant strategy [1]; some projects just =
can't be built for i386, leaving only the x86_64 arch and making testing =
the universal variant impossible. But please take this message as a =
reminder to check your ports for the ability to build universal where =
possible (i.e. for software that does build for i386 and if you have a =
system with macOS 10.13 or earlier and Xcode 9 or earlier). I have been =
installing all ports with the universal variant for years and I try to =
file bug reports when I can, but I'm probably not installing every port =
so I haven't tested everything.

Most ports automatically use the right compiler [2] and -arch flags =
because they use a standard build system like automake or cmake. If your =
port doesn't use the right compiler or if you fixed it to use the right =
compiler but didn't also fix it to use the right -arch flags, please fix =
that now; you can verify correctness on any OS version by looking at the =
MacPorts log of building your port and verifying that the correct =
compiler is invoked (i.e. "/usr/bin/clang" not "gcc") and that (almost) =
every invocation of the compiler also has -arch flags. The new makefile =
1.0 portgroup can help do this for ports that don't have a configure =
phase.

Also, if your ports do something different depending on the architecture =
and have if statements or switch statements based on the architecture, =
be prepared for needing to modify that in the future to accommodate =
architecture values other than the current i386 ppc ppc64 x86_64 =
quartet.

[1] https://trac.macports.org/ticket/59864
[2] https://trac.macports.org/wiki/UsingTheRightCompiler=
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