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From: Simon Wright <simon@pushface.org>
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Subject: Re: components_4_64 python Test_Class Build Fails
Date: Fri, 21 Oct 2022 20:56:54 +0100
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> BTW, what are you "posh guys" (:-)) are going to do with M1/2? Is
> there GNAT?
>
> Is there any noticeable differences to X86_64 on the Ada level?
> Endianness must be same, correct? Alignment/padding inside C
> structures when interfacing to Ada?

The Macs with Apple silicon (I don't think there's a difference between
M1 & M2 at our level) support, for an unknown number of future OS
iterations, a feature called Rosetta (2) which effectively does
just-in-time translation of x86_64 binaries to aarch64. This is the same
scheme they had for the Power -> Intel transition.

x86_64 GCCs run just fine on Apple silicon, generating x86_64 binaries;
I just ran the Alire gnatprove on my M1 mac mini and it failed in the
same way as on x86_64 (libgmp not where it was expected).

We have a native aarch64 compiler that generates aarch64 binaries, no
noticable difference* (maybe if you got out a stopwatch ...). The only
trouble is that aarch64 binaries can't use x86_64 shared libraries; the
assembler, linker and libraries that Apple provides are
dual-architecture, and some external providers provide the same or offer
the choice at download time.

* a couple of ACATS tests designed to check Storage_Error failed on M1 -
  I don't remember how.