Possible to restore ppc64 support to 10.6? What needed? I can test

[barracuda156]

@iains Opening this topic now, since if it could be done, earlier the better (I will need to rebuild much stuff).

Specifically, I am interested to know the following:

1. Is it feasible in principle, given resources we have? I do not expect anyone do this work for me, of course, but if you could give me an idea what to try, I will test that. I have a clone of my 10A190 installation where I can experiment and see what works. I have also 10.5.8 PPC installation (where I built gcc10) and now 10.6.8 x86_64 installation (for cross-compiling).
2. From what I found out in my cross-compiling experiment (to be continued), apparently it is possible to build for ppc64 against 10.6 SDK from 10A190 after replacing 2–3 dylib files. At this moment I cannot verify if that will work in a sense that resulting binaries will function (I ran into other issues with cross-compiler), but I got rid of arch-related errors.
3. Is being able to run ppc64 apps equivalent to being able to compile for ppc64 natively? Or these two are unrelated? (Sorry, if a silly question. I am not an expert here, but I am learning.) I ask this, since building for ppc64 could perhaps be done either on 10.5.8 or 10.6.8, provided 10.6 PPC will be able to use those binaries.

P. S. Aside of 10.6 builds and respective Xcodes, we got Kernel Debug Kits (for most of available builds), if that matters.
Xcode and Unix tools could be functional on PowerPC way beyond 10A190. I can confirm that Xcode and gcc from 10A222 work (need replacing ld and gnumake with ones from 10A190), and it looks like it may work with 10A261 and 10A286 too.
P. P. S. @kencu probably lost interest in 10.6 PPC, but I will be happy if he joins.

[iains]

The primary barrier is that large (and important) parts of the system are closed source - so, in general, we cannot just rebuild them to have a ppc64 slice.

The work to make a 64b kernel and the device drivers for it would be huge (so I'd say realistically you would have to accept the same basis as 10.5.8 - 32b kernel capable of 64b exes).

So .. I suspect that you might be able to make a hybrid (although it seems that many of the 10.5.8 builds are actually newer than the working ppc 10.6 installs) ...

.. of course, it's all "just code" so someone could replicate the missing or non-published parts - but the size of the project ...

[barracuda156]

@iains

so I'd say realistically you would have to accept the same basis as 10.5.8 - 32b kernel capable of 64b exes).

Yes, same basis as 10.5.8 is perfectly okay, if it is achieved.

So .. I suspect that you might be able to make a hybrid (although it seems that many of the 10.5.8 builds are actually newer than the working ppc 10.6 installs) ...

It’s a mix. Some components are newer in 10.5.8 and some are newer in 10A190. Some comparison is listed here (see TABLE 4. EXPERIMENTAL: Bringing in & testing newer elements from 10.5.8): https://forums.macrumors.com/threads/snow-leopard-on-unsupported-ppc-machines.2232031/

[barracuda156]

@iains Could you say which components in 10.5 are responsible for ppc64 support? If that is something known.
Not necessarily a complete list, but at least types.

I can identify which components had ppc64, which was then removed in 10.6, but it is not obvious if all of such are actually needed. We rather not replace components unnecessarily, I guess.

BTW – repeating here – Apple began removing ppc64 already in 10.5.x. So something perhaps have to be sourced from earlier builds of 10.5.
Example: QT, GLUT and OpenGL frameworks
https://groups.google.com/g/hugin-ptx/c/iSC6IbFfEP0

[barracuda156]

Trying to build 64-bit helloworld gives this:

36-195% gcc /Users/svacchanda/HelloWorld.c -o hello -m64
ld warning: in /usr/lib/crt1.10.5.o, missing required architecture ppc64 in file
ld warning: in /usr/lib/libgcc_s.10.5.dylib, missing required architecture ppc64 in file
ld warning: in /usr/lib/libSystemStubs.a, missing required architecture ppc64 in file
ld warning: in /usr/lib/libSystem.dylib, missing required architecture ppc64 in file
Undefined symbols:
  "_puts", referenced from:
      _main in ccwqJZbE.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

I have tried to replace these files with ones from 10.5.8. Unfortunately, 10A190 doesn’t boot after that: white screen with Apple and fans to full speed.

@iains @kencu Does this mean we are out of luck here or something else may be tried?

[iains]

Trying to build 64-bit helloworld gives this:

ld warning: in /usr/lib/libSystem.dylib, missing required architecture ppc64 in file```

@iains @kencu Does this mean we are out of luck here or something else may be tried?

Yup, IMO it's a non-starter, you would not expect to be able to bring the 10.5.8 libSystem / libgcc_s into 10.6.
missing ppc64 slices in critical system components that are not fully open-sourced is a show-stopper, we cannot even rebuild.

So .. you could carry on with ppc only, but not sure of the merit TBH.

Iff I had the time, (which I don't given other commitments) I would invest it in making a 10.5.9 where we rebuild packages that are OSS to fix bugs and/or other issues in 10.5.8 - e.g. we could install modern libgcc_s and libstdc++ which would immediately bring some advantages,.. but as said, right now I don't have the time.

[barracuda156]

Yup, IMO it's a non-starter, you would not expect to be able to bring the 10.5.8 libSystem / libgcc_s into 10.6. missing ppc64 slices in critical system components that are not fully open-sourced is a show-stopper, we cannot even rebuild.

Got it, thank you. For now, we can consider this topic closed. (Please keep this discussion though, just in case something is discovered later on.)

So .. you could carry on with ppc only, but not sure of the merit TBH.

Well, I will keep 10A190 and try improving what is improvable. There might be some benefits to having it: for example, I had tbb built on it when the same failed on 10.5.8.

Iff I had the time, (which I don't given other commitments) I would invest it in making a 10.5.9 where we rebuild packages that are OSS to fix bugs and/or other issues in 10.5.8 - e.g. we could install modern libgcc_s and libstdc++ which would immediately bring some advantages,.. but as said, right now I don't have the time.

If you ever get back to that, would be awesome.