C ++ 20库对xcode 12的支持 [英] c++20 library support for xcode 12

问题描述

我可以在xcode 12中使用c ++ 20库吗?(xcode 12 beta 5，clang版本10.0.0).

因此在xcode构建设置中，而不是

xcode构建设置中的

 //，"c ++标准库"CLANG_CXX_LIBRARY = libc ++ 

也许使用类似的东西(不起作用=> clang err:无效的库名)

  CLANG_CXX_LIBRARY = libc ++ 20//例如.libc ++ 20和libc ++ 2a是无效的名称 

我已经设置(可以通过提供c ++ 20 语言支持来工作，但是不提供c ++ 20 library 支持)

xcode构建设置中的

 //，"c ++语言方言"CLANG_CXX_LANGUAGE_STANDARD = c ++ 2a//可以，但是不提供c ++ 20库 

我知道c ++ 20库尚未完成/尚未正式发布.

问题:

您知道在xcode 12中使用(初步)c ++ 20库的任何(简便)方法吗?

谢谢

解决方案

可能有更简单的方法，或者我可能做了多余的事情(让我知道可以删除的内容)，但这是一个肯定的方法.

使用

构建llvm

  cmake -G"Sublime Text 2-Ninja"-DCMAKE_BUILD_TYPE =发布\-DLLVM_ENABLE_PROJECTS ="clang; libcxx; libcxxabi" -DCMAKE_CXX_STANDARD = 17 -DLLVM_INCLUDE_TESTS = OFF \-DLLVM_TARGETS_TO_BUILD = X86 -DLLVM_CCACHE_BUILD = ON -DLLVM_CREATE_XCODE_TOOLCHAIN = ON \-DCMAKE_INSTALL_PREFIX =易于清洁的位置" \-DLLVM_ENABLE_RTTI =关闭\../llvm 

• 正常构建项目.但是，由于禁用了索引编制，因此在代码成功构建时，警告可能不会消失.:(添加标题搜索路径有助于警告.

  • 将系统标头搜索路径添加到Xcode

  ---

  确保检查功能状态:

  • http://clang.llvm.org/cxx_status.html
  • https://en.cppreference.com/w/cpp/20

  我测试过的代码:

    #include< compare>#include< concepts>struct Aggr {我字符c;自动运算符< =>(Aggr const&)const =默认值;};结构A {int x;int y;int z;};int main(){//A a {.y = 2，.x = 1};//错误;指定者订单与声明不符//命令a b {.x = 1，.z = 2};//好的，b.y初始化为0返回0;} 

  can i use the c++20 library with xcode 12? (xcode 12 beta 5, with clang version 10.0.0).

  so in xcode build settings, instead of

  // in xcode build settings, "c++ standard library"
  CLANG_CXX_LIBRARY = libc++
  

  maybe use something like (does not work => clang err: invalid library name)

  CLANG_CXX_LIBRARY = libc++20 // eg. libc++20 & libc++2a are invalid names
  

  i have already set (works by providing c++20 language support, but does not provide c++20 library support)

  // in xcode build settings, "c++ language dialect"
  CLANG_CXX_LANGUAGE_STANDARD = c++2a // ok but does not provide c++20 library
  

  im aware that the c++20 library is not yet complete/officially released.

  question:

  do you know of any (easy) way to use the (preliminary) c++20 library with xcode 12?

  thanks

  解决方案

  There can be easier ways, or I might have done something redundant (let me know what can be removed), but here's a surefire way.

  Build llvm with

  cmake -G "Sublime Text 2 - Ninja" -DCMAKE_BUILD_TYPE=Release \
  -DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi" -DCMAKE_CXX_STANDARD=17 -DLLVM_INCLUDE_TESTS=OFF \
  -DLLVM_TARGETS_TO_BUILD=X86 -DLLVM_CCACHE_BUILD=ON -DLLVM_CREATE_XCODE_TOOLCHAIN=ON \
  -DCMAKE_INSTALL_PREFIX="easy to clean location"\
  -DLLVM_ENABLE_RTTI=OFF \
  ../llvm
  

  • http://clang.llvm.org/get_started.html
  • https://llvm.org/docs/CMake.html

  libcxxabi is required or linking libcxx will fail with:

  ld: library not found for -lcxxabi_shared clang: error: linker command failed with exit code 1 (use -v to see invocation)

  DLLVM_CCACHE_BUILD requires https://ccache.dev (use brew if you wish). First build will be very slow. Rebuilds will be faster.

  ---

  After the above is done and ninja compiles around 3000 files, run

   ninja install all 
   ninja install build-xcode-toolchain
  

  Find the created toolchain in location you chose above/Toolchains. Copy it to ~/Library/Developer/Toolchains/

  ---

  If Xcode is open, close it and reopen. In Xcode app menu > Toolchains > choose the new one, llvm12git.

  Create a new c++ project normally and go to its project's build settings.

  Search for COMPILER_INDEX_STORE_ENABLE or Enable index-while-building functionality and set it to "No". Otherwise, build fails with "unrecognised option" about indexing.

  ---

  Change "C++ language dialect" to "c++20" or "c++2a"

  Build the project normally. However, warnings may not go away while the code successfully builds due to indexing disabled. :( Adding header search path helps with warnings.

  • Adding system header search path to Xcode

  ---

  Make sure to check feature status:

  • http://clang.llvm.org/cxx_status.html
  • https://en.cppreference.com/w/cpp/20

  Code I tested:

  #include <compare>
  #include <concepts>
  
  struct Aggr {
    int i;
    char c;
  
    auto operator<=>(Aggr const &) const = default;
  };
  struct A {
    int x;
    int y;
    int z;
  };
  int main()
  {
  
    // A a{.y = 2,.x = 1};  // error; designator order does not match declaration
    // order
    A b{.x = 1, .z = 2};  // ok, b.y initialized to 0
    return 0;
  
  }
  

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