为什么安装Xcode命令行工具会改变'gcc --version'报告的内容 [英] Why did installing Xcode command line tools change what 'gcc --version' reports

问题描述

最近，我通过AppStore将OS 10.9上的Xcode更新到5.0.1版。在我看来，这个更新也更新了命令行工具，例如运行 gcc --version 生成的

<$ p $配置文件：--prefix = / Applications / Xcode.app / Contents / Developer / usr --with-gxx-include-dir = / Applications / Xcode.app / Contents / Developer / Platforms / MacOSX.platform / Developer / SDKs / MacOSX10.9.sdk / usr / include / c ++ / 4.2.1
Apple LLVM 5.0版（clang-500.2.79）（基于LLVM 3.3svn）
目标：x86_64-apple-darwin13.0.0
线程模型：posix

然而 SE在此处的表明情况并非如此，命令行工具需要单独下载和安装。我做到了这一点，并以相同的工具版本结束，但有细微的差异。例如，现在正在运行 gcc --version 产生

  gcc  - -version 
配置：--prefix = / Applications / Xcode.app /目录/ Developer / usr --with-gxx-include-dir = / usr / include / c ++ / 4.2.1 
 Apple LLVM 5.0版（clang-500.2.79）（基于LLVM 3.3svn）
目标：x86_64-apple-darwin13.0.0 
线程模型：posix 
  

这是事情应该如何工作的吗？这是否代表当前Xcode命令行工具的预期行为，还是它通过直接下载安装的特性？ 。通过AppStore与Xcode一起安装;如果甚至可能的话）？

从 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/的变化有什么意义MacOSX10.9.sdk / usr / include / c ++ / 4.2.1 至 / usr / include / c ++ / 4.2.1 ？

解决方案

我会用列表来组织我的答案，这样您就可以得到完整的图片，您的主要问题的答案会在最后结束列表项：

• 自从Mavericks以来，默认的编译器套件是Clang / LLVM而不是GNU GCC。为了保持后向兼容性，分别指向Clang和Clang ++的 gcc 和 g ++ 的同义词已被保留下来，是非常向后兼容的GCC，没有理由不这样做。


• 自从XCode 6我认为，XCode自动捆绑命令行开发工具在主要安装和。 XCode中。默认框架和工具包也一样。完整的命令行开发在这一点上还没有完全实现，只是启用了XCode开发。
然而，为了在命令行上成功进行开发，必须执行 xcode-select --install ，然后按照说明操作。


• 鉴于现在SDK已经捆绑并组织在一个目录结构中在XCode.app包内部，你注意到的gxx-include-dir中的变化是由于现在/ usr / include仅仅是一个软链接，现在已经到了特定包含的适当位置：
  
  

  
  

  $ ls -l / usr / include
  
  lrwxr-xr-x 1个根轮112 Feb 2 19 ：08 / usr / include - > /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include /

  
  

最后一点，不一定是坏事， xcode-select（1）命令现在可以用来管理acti ve SDK。
我希望这会让那些困惑的人澄清一些事情，因为所有这些（相当大的）变化都是以完全沉默的方式以经典的苹果时尚推出的。

Recently I updated Xcode on OS 10.9 to version 5.0.1 through the AppStore. It appeared to me that this update also updated command line tools, for example running gcc --version produced

Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/c++/4.2.1
Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.0.0
Thread model: posix

However answers here on SE indicate that this is not the case and that command line tools need to be downloaded and installed separately. I did this and ended up with the same tool versions, but with subtle differences. For example, now running running gcc --version produces

gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.0.0
Thread model: posix

Is this how things are supposed to work — does this represent the expected behavior for current Xcode command line tools or is it peculiar to an installation via direct download (vs. installing along with Xcode through the AppStore; if that's even possible)?

And what's the significance of the change from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/c++/4.2.1 to /usr/include/c++/4.2.1?

解决方案

I'll structure my answer with a list so that you get the full picture, the answer to your main question being concluded in the last list item:

• Since Mavericks, the default compiler suite has been Clang/LLVM instead of GNU GCC. Synonyms for gcc and g++ that point to Clang and Clang++ respectively have been kept in order to preserve backwards compatibility and since Clang is very much backwards compatible with GCC, there's no reason not to do so.
• Since XCode 6 I think, XCode automatically bundles the command line developer tools in the main install and .app bundle for XCode. Same goes for default frameworks and toolkits. Full command line development is still not fully operational at this point, just enabled XCode development.
• However, in order to successfully do development at the command line one has to execute xcode-select --install in the Terminal app and follow the instructions.

• Given that the SDK's are now bundled and organized in a directory structure inside XCode.app bundle, the change in gxx-include-dir you noticed is due to the fact that now, /usr/include is merely a soft link now to the proper place for the specific includes:

  $ls -l /usr/include

  lrwxr-xr-x 1 root wheel 112 Feb 2 19:08 /usr/include -> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include/

The last point, is not necessarily a bad thing and xcode-select(1) command can now be used to manage the active SDK. I hope this clarifies things a bit for those confused, since all these (quite big) changes were rolled out in classic Apple fashion, in complete and utter silence.

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