Re: [Tarantool-patches] [PATCH luajit 2/3] macOS: Workaround for buggy XCode 15.0 - 15.2 linker.

[Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Hi, Sergey!
Thanks for the review!

See my answers below.

On 26.11.25, Sergey Bronnikov wrote:
> Hi, Sergey,
> 
> thanks for the patch! LGTM with a minor comment.
> 
> Sergey
> 
> On 11/24/25 23:26, Sergey Kaplun wrote:
> > From: Mike Pall <mike>
> >
> > Thanks to Carlo Cabrera.
> >
> > (cherry picked from commit b2915e9ab55b999429b4d1931097064c4e17de53)
> >
> > The previous commit removes emitting the `.subsections_via_symbols` [1]
> > directive for macOS. Nevertheless, the aforementioned Xcode linker
> > versions produce incorrect code for the VM without this directive.
> >
> > As a fix for old versions of macOS, this patch adds emitting this
> I would add exact macOS versions, according to [1] it is: 15000000
> 1. 

As discussed offline, this is exactly the problem with the Xcode
version, and this macro specifies the corresponding Xcode versions.

> https://stackoverflow.com/questions/19387043/how-can-i-reliably-detect-the-version-of-clang-at-preprocessing-time#comment137533353_19391724 
> 
> > directive in the buildvm.
> >
> > [1]:https://reviews.llvm.org/D79926
> >
> > Sergey Kaplun:
> > * added the description for the problem
> >
> > Part of tarantool/tarantool#11691

I've added the link to the machO format as you suggested:

| macOS: Workaround for buggy XCode 15.0 - 15.2 linker.
|
| Thanks to Carlo Cabrera.
|
| (cherry picked from commit b2915e9ab55b999429b4d1931097064c4e17de53)
|
| The previous commit removes emitting the `.subsections_via_symbols`
| [1][2] directive for macOS. Nevertheless, the aforementioned Xcode linker
| versions produce incorrect code for the VM without this directive.
|
| As a fix for old versions of macOS, this patch adds emitting this
| directive in the buildvm.
|
| [1]: https://reviews.llvm.org/D79926
| [2]: https://github.com/aidansteele/osx-abi-macho-file-format-reference
|
| Sergey Kaplun:
| * added the description for the problem
|
| Part of tarantool/tarantool#11691

> > ---
> >   src/host/buildvm_asm.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/src/host/buildvm_asm.c b/src/host/buildvm_asm.c
> > index 43595b31..fc09d71a 100644
> > --- a/src/host/buildvm_asm.c
> > +++ b/src/host/buildvm_asm.c
> > @@ -347,6 +347,10 @@ void emit_asm(BuildCtx *ctx)
> >       fprintf(ctx->fp, "\t.ident \"%s\"\n", ctx->dasm_ident);
> >       break;
> >     case BUILD_machasm:
> > +#if defined(__apple_build_version__) && __apple_build_version__ >= 15000000 && __apple_build_version__ < 15000300
> > +    /* Workaround for XCode 15.0 - 15.2. */
> 
> __apple_build_version__ defines a macOS version. But macOS 15 includes 
> XCode 16, see [2], not 15.x
> 
> So there is an inconsistency in condition and comment. I would list 
> macOS versions in a comment like this
> 
> "Workaround for macOS 15, 15.1 and 15.2" to avoid misinterpretation due 
> to non-strict inequality with 15000300.
> 
> Also, I would include a link to [2] to the commit message.
> 
> 2. 
> https://developer.apple.com/documentation/macos-release-notes/macos-15-release-notes

The same about the comment above.

> 
> > +    fprintf(ctx->fp, "\t.subsections_via_symbols\n");
> > +#endif
> >       fprintf(ctx->fp,
> >         "\t.cstring\n"
> >         "\t.ascii \"%s\\0\"\n", ctx->dasm_ident);

-- 
Best regards,
Sergey Kaplun