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The article references a few compiler extensions: __builtin_xnu_type_signature, __builtin_xnu_type_summary, and the xnu_usage_semantics attribute. I can see re

The article references a few compiler extensions: __builtin_xnu_type_signature, __builtin_xnu_type_summary, and the xnu_usage_semantics attribute. I can see references to these builtins in the latest xnu source[1], but not in upstream llvm[2], or Apple's forks of llvm[3] and clang[4]. It's been possible to build your own XNU[5] for a long time. Is that still possible now? [1]: https://github.com/apple-oss-distributions/xnu [2]: https://github.com/llvm/llvm-project [3]: https://github.com/apple-oss-distributions/llvmCore [4]: https://github.com/apple-oss-distributions/clang [5]: https://kernelshaman.blogspot.com/2021/02/building-xnu-for-macos-112-intel-apple.html

saagarjha 4y ago
I believe Apple’s toolchain ship with this.
- davidbalbert 4y ago
  You're right. Just compiled the following program with clang from Xcode 14 (Apple clang version 14.0.0 (clang-1400.0.29.102)) without issue. #include <stdio.h> struct foo { uintptr_t p __attribute__((xnu_usage_semantics("pointer"))); }; int main() { struct foo f = { 100 }; printf("%lu\n", f.p); return 0; } Doesn't seem -Wxnu-typed-allocators (which I forgot to mention above) is present in my version. Didn't test the others. I also just realized that the latest tagged release of https://github.com/apple-oss-distributions/clang https://github.com/apple-oss-distributions/clang is 800.0.38, my clang is reporting 1400.0.29.102. Is Apple no longer releasing the source for their compilers?
  - MBCook 4y ago
    The article sounded to me like Apple had a private fork with extra tooling to help with their kernel work.
    - cbsmith 4y ago
      Heh... and it was just a few weeks ago I was assured that all of the platform internals were fully open sourced. ;-)
      - pjmlp 4y ago
        I doubt that they have opened the custom C compiler used in iBoot for example. https://support.apple.com/guide/security/memory-safe-iboot-implementation-sec30d8d9ec1/web https://support.apple.com/guide/security/memory-safe-iboot-i...
        saagarjha 4y ago
        They have not.
      - roblabla 4y ago
        A lot of the internals are, but certainly not all. And they always lag behind with what is currently released, sometimes by several months.
        cbsmith 4y ago
        It's funny, that's pretty much what I said...
  - saagarjha 4y ago
    The clang that ships in Xcode uses fake version numbers, but yes, some of it remains proprietary.
  - pjmlp 4y ago
    Apple never did release everything that their compilers do, that is why cppreference has a column for Apple's clang, and why watchOS can use bitcode as binary format, even though the official LLVM bitcode isn't stable.

saagarjha 4y ago

I believe Apple’s toolchain ship with this.

davidbalbert 4y ago
You're right. Just compiled the following program with clang from Xcode 14 (Apple clang version 14.0.0 (clang-1400.0.29.102)) without issue. #include <stdio.h> struct foo { uintptr_t p __attribute__((xnu_usage_semantics("pointer"))); }; int main() { struct foo f = { 100 }; printf("%lu\n", f.p); return 0; } Doesn't seem -Wxnu-typed-allocators (which I forgot to mention above) is present in my version. Didn't test the others. I also just realized that the latest tagged release of https://github.com/apple-oss-distributions/clang https://github.com/apple-oss-distributions/clang is 800.0.38, my clang is reporting 1400.0.29.102. Is Apple no longer releasing the source for their compilers?
- MBCook 4y ago
  The article sounded to me like Apple had a private fork with extra tooling to help with their kernel work.
  - cbsmith 4y ago
    Heh... and it was just a few weeks ago I was assured that all of the platform internals were fully open sourced. ;-)
    - pjmlp 4y ago
      I doubt that they have opened the custom C compiler used in iBoot for example. https://support.apple.com/guide/security/memory-safe-iboot-implementation-sec30d8d9ec1/web https://support.apple.com/guide/security/memory-safe-iboot-i...
      - saagarjha 4y ago
        They have not.
    - roblabla 4y ago
      A lot of the internals are, but certainly not all. And they always lag behind with what is currently released, sometimes by several months.
      - cbsmith 4y ago
        It's funny, that's pretty much what I said...
- saagarjha 4y ago
  The clang that ships in Xcode uses fake version numbers, but yes, some of it remains proprietary.
- pjmlp 4y ago
  Apple never did release everything that their compilers do, that is why cppreference has a column for Apple's clang, and why watchOS can use bitcode as binary format, even though the official LLVM bitcode isn't stable.