Re: Sharing patch with externals on MacOS

IOhannes m zmölnig via Pd-list <[email protected]> Sun, 12 Apr 2026 17:11:01 +0200

Newsgroups	gmane.comp.multimedia.puredata.general
Message-ID	<[email protected]>

On 12/04/2026 14:43, João Pais wrote:
> lipo -remove arm64 [remove the need to activate rosetta when running the
> standalone with pd~]

are you sure about that?

my impression was, that *rosetta* is a run-time emulation of a different
CPU. e.g. if you have a i386 CPU but your old binary is PowerPC only,
then rosetta will translate the PowerPC instructions to i386 on-the-fly.
(that's obviously a historic example; these days you typically have
rosetta2 for amd64-only binaries that need to run on arm64 CPUs; but the
names are easier to read in the historic example).

now, *fat* binaries are something different.
a fat binary for both PowerPC *and* i386 will contain the native
instructions for both PowerPC and i386.
so when opening the file on your shiny new i386, you do not need rosetta
at all, because the i386 instructions are already there.
and if you open the same binary on the PowerPC, you also have the native
instructions.
fat binaries are not limited to certain architectures. theoretically you
can have a fat binary for powerpc, i386, amd64 and arm64, wihch will run
- without rosetta - on any Apple that was sold in the last 25 years.

TL;DR fat binaries are a way to provide binaries that are executable
natively on multiple CPU families. conversely, rosetta(2) is a system
that allows you to run a binary for a different CPU on your system.
fat binaries take more space (files for a 2-arch fat binary are about
twice the size as a single-arch binary). rosetta takes more CPU-cycles
(emulating a different CPU-architecture is rather costy).

so when you issue
```
lipo -remove arm64
```
then you are effectively removing the native instructions for arm64 from
your binary.

assuming that your target audience has recentish Apple machines (which
all come with arm64 processors), then you are effectively *forcing*
rosetta on them.

(and it seems that Apple started to fade out rosetta(2), targetting
"late 2027" for a complete removal)

fmdsar
IOhannes

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