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Apple's LLVM and Clang from Xcode 9 are based on version 4.0 of the main LLVM/Clang. You'll need at least LLVM/Clang 5.0 for more C++17 compatibility. To be fa

Apple's LLVM and Clang from Xcode 9 are based on version 4.0 of the main LLVM/Clang. You'll need at least LLVM/Clang 5.0 for more C++17 compatibility. To be fair, modern C++ support is not a priority for Apple, their efforts are more toward Swift.

cozzyd 9y ago
It's fine if it's not a priority, but why ship a crippled compiler when they could ship the upstream compiler? ABI issues maybe? (I've heard from OS X users that XCode updates have broken the string ABI multiple times anyway...). I don't really care too much since I'm not an OS X user, but some people insist on trying to compile/run some of the software I work on on OS X...
- Joky 9y ago
  Talking of Apple Clang as a crippled compiler comes across as very uneducated opinion to me. It goes through an extensive validation / stabilization for many months before being released. So yes it adds some delay in getting new shiny features, but calling it "crippled" seems like a very much uneducated opinion here. You can have an idea about the integration exactly what version from upstream Apple is integrating by looking at Swift (they somehow have to be in sync). I guess the last Xcode update was: https://github.com/apple/swift-clang/commits/swift-4.1-branch https://github.com/apple/swift-clang/commits/swift-4.1-branc... The next minor update will likely be this one: https://github.com/apple/swift-clang/commits/swift-4.2-branch https://github.com/apple/swift-clang/commits/swift-4.2-branc... ; so judging at the history I bet you'll get a version of clang that is based of clang-5.0 upstream. And likely the next major Xcode (10?) would be based of this: https://github.com/apple/swift-llvm/tree/swift-5.0-branch https://github.com/apple/swift-llvm/tree/swift-5.0-branch ; which is based off clang-6.0. Note that this branch will very likely get many bug fixes in the next ~6 months. (the above are only guesses based on past release, I don't know anything about their current plan or schedule). The Apple engineers will try to build all variants of the Apple OS for all the HW they ship with this new clang-6.0 based branch. The usual process is to fix upstream the development of clang-7.0 and cherry-pick in these branches. So the compiler that you'll get with the next major Xcode, even if based of clang-6.0 will have many/most of the bug-fixes that will be in clang-7.0 (release in July), but not most of the new features (and new bugs!). Caveat: this apply only to ARM64 and X86, of course Apple does not try to backport bugfixes for platform they don't support. (Note that libc++ is handled a bit differently.) Disclaimer: I was part of the Apple clang team until ~1y ago.
  - cozzyd 9y ago
    I'm sure a lot of work goes into it, but often features that are present in upstream clang seem to be removed or heavily delayed. Fom the perspective of a Linux "developer" whose software (C++ scientific tools) sometimes gets compiled with the Xcode clang++, I've seen (i.e. been told of by Apple users) all sorts of problems that don't happen with upstream clang or modern gcc. The fact that the versioning isn't coherent with upstream clang makes things even more confusing.
    - pertymcpert 9y ago
      What features?
      - cozzyd 9y ago
        Well the one I'm familiar with is Apple's explicit disabling of thread-local storage for a long time. See e.g. https://stackoverflow.com/a/23850891 https://stackoverflow.com/a/23850891, which thankfully has been fixed since then (but it took something like 2 years).
  - m1h4 9y ago
    Thank you for the info/insight. I assumed that the specified language features, especially ones also depending on core libraries like libc++, would most likely be released as part of the next major OS update (since these are very essential for the complete system and need to be tested along side it as one whole). I didn't check the macOS 10.13.4 beta, but I'm assuming that the features I mentioned are coming as part of macOS 10.14 and Xcode 10.
- BozeWolf 9y ago
  Can’t you just install a more up to date compiler with brew? I don’t know if signing binaries works though.
  - gumby 9y ago
    Brew's approach to compilers adds tremendous friction. Brew doesn't download a binary, it builds the compilers (both gcc and clang) and installs them but doesn't make bin/ links. It's because of this that our build process (I'm not OP BTW) builds with all of brew gcc, brew clang and xcode (thank goodness for xcodebuild at least, so I can do this all from a Makefile). CMake is really helpful here.
    - saagarjha 9y ago
      Homebrew has bottles so you don't have to do compilation on your machine–you just download a precompiled version.
      - gumby 9y ago
        Yes, but GCC and clang are not provided that way, and, as I mentioned, not linked into /usr/local/bin. I understand why they don't do the latter (it could confuse the unsuspecting user) but it does add friction.
        saagarjha 9y ago
        > but GCC and clang are not provided that way What? On my machine both are available as bottles: $ brew info gcc | head -n 1 gcc: stable 7.3.0 (bottled), HEAD $ brew info llvm | head -n 1 llvm: stable 5.0.1 (bottled), HEAD [keg-only]
        gumby 9y ago
        Huh, interesting; our site config seems to require building so I had assumed that was the case!
- abritinthebay 9y ago
  "crippled" is rather hyperbolic. Older, less feature rich, but not crippled.
saagarjha 9y ago
> Apple's LLVM and Clang from Xcode 9 are based on version 4.0 of the main LLVM/Clang. How do you know this? Is this documented anywhere?

cozzyd 9y ago

It's fine if it's not a priority, but why ship a crippled compiler when they could ship the upstream compiler? ABI issues maybe? (I've heard from OS X users that XCode updates have broken the string ABI multiple times anyway...). I don't really care too much since I'm not an OS X user, but some people insist on trying to compile/run some of the software I work on on OS X...

Joky 9y ago
Talking of Apple Clang as a crippled compiler comes across as very uneducated opinion to me. It goes through an extensive validation / stabilization for many months before being released. So yes it adds some delay in getting new shiny features, but calling it "crippled" seems like a very much uneducated opinion here. You can have an idea about the integration exactly what version from upstream Apple is integrating by looking at Swift (they somehow have to be in sync). I guess the last Xcode update was: https://github.com/apple/swift-clang/commits/swift-4.1-branch https://github.com/apple/swift-clang/commits/swift-4.1-branc... The next minor update will likely be this one: https://github.com/apple/swift-clang/commits/swift-4.2-branch https://github.com/apple/swift-clang/commits/swift-4.2-branc... ; so judging at the history I bet you'll get a version of clang that is based of clang-5.0 upstream. And likely the next major Xcode (10?) would be based of this: https://github.com/apple/swift-llvm/tree/swift-5.0-branch https://github.com/apple/swift-llvm/tree/swift-5.0-branch ; which is based off clang-6.0. Note that this branch will very likely get many bug fixes in the next ~6 months. (the above are only guesses based on past release, I don't know anything about their current plan or schedule). The Apple engineers will try to build all variants of the Apple OS for all the HW they ship with this new clang-6.0 based branch. The usual process is to fix upstream the development of clang-7.0 and cherry-pick in these branches. So the compiler that you'll get with the next major Xcode, even if based of clang-6.0 will have many/most of the bug-fixes that will be in clang-7.0 (release in July), but not most of the new features (and new bugs!). Caveat: this apply only to ARM64 and X86, of course Apple does not try to backport bugfixes for platform they don't support. (Note that libc++ is handled a bit differently.) Disclaimer: I was part of the Apple clang team until ~1y ago.
- cozzyd 9y ago
  I'm sure a lot of work goes into it, but often features that are present in upstream clang seem to be removed or heavily delayed. Fom the perspective of a Linux "developer" whose software (C++ scientific tools) sometimes gets compiled with the Xcode clang++, I've seen (i.e. been told of by Apple users) all sorts of problems that don't happen with upstream clang or modern gcc. The fact that the versioning isn't coherent with upstream clang makes things even more confusing.
  - pertymcpert 9y ago
    What features?
    - cozzyd 9y ago
      Well the one I'm familiar with is Apple's explicit disabling of thread-local storage for a long time. See e.g. https://stackoverflow.com/a/23850891 https://stackoverflow.com/a/23850891, which thankfully has been fixed since then (but it took something like 2 years).
- m1h4 9y ago
  Thank you for the info/insight. I assumed that the specified language features, especially ones also depending on core libraries like libc++, would most likely be released as part of the next major OS update (since these are very essential for the complete system and need to be tested along side it as one whole). I didn't check the macOS 10.13.4 beta, but I'm assuming that the features I mentioned are coming as part of macOS 10.14 and Xcode 10.
BozeWolf 9y ago
Can’t you just install a more up to date compiler with brew? I don’t know if signing binaries works though.
- gumby 9y ago
  Brew's approach to compilers adds tremendous friction. Brew doesn't download a binary, it builds the compilers (both gcc and clang) and installs them but doesn't make bin/ links. It's because of this that our build process (I'm not OP BTW) builds with all of brew gcc, brew clang and xcode (thank goodness for xcodebuild at least, so I can do this all from a Makefile). CMake is really helpful here.
  - saagarjha 9y ago
    Homebrew has bottles so you don't have to do compilation on your machine–you just download a precompiled version.
    - gumby 9y ago
      Yes, but GCC and clang are not provided that way, and, as I mentioned, not linked into /usr/local/bin. I understand why they don't do the latter (it could confuse the unsuspecting user) but it does add friction.
      - saagarjha 9y ago
        > but GCC and clang are not provided that way What? On my machine both are available as bottles: $ brew info gcc | head -n 1 gcc: stable 7.3.0 (bottled), HEAD $ brew info llvm | head -n 1 llvm: stable 5.0.1 (bottled), HEAD [keg-only]
        gumby 9y ago
        Huh, interesting; our site config seems to require building so I had assumed that was the case!
abritinthebay 9y ago
"crippled" is rather hyperbolic. Older, less feature rich, but not crippled.

saagarjha 9y ago

> Apple's LLVM and Clang from Xcode 9 are based on version 4.0 of the main LLVM/Clang. How do you know this? Is this documented anywhere?