问题描述
我想今天的问题是哪个" c ++编译器是Mac上的默认编译器?
I guess the question of the day is "which" c++ compiler is the default on mac?
如果我执行xcrun -find c++，则表示它在/Applications/Xcode.app/etc...中.
If I do xcrun -find c++ it says it's in /Applications/Xcode.app/etc....
当我在Xcode目录中搜索tr1/unordered_map时，它就在那里.
When I search the Xcode directory for tr1/unordered_map, it's there.
所以我很困惑.为什么我收到一个显示fatal error: 'tr1/unordered_map' file not found的构建错误?
So I'm confused. Why am I getting a build error that says fatal error: 'tr1/unordered_map' file not found?
推荐答案
简短的回答:使用-stdlib=libstdc++调用clang ++，并且tr1标头会在那里.
Short answer: call clang++ with -stdlib=libstdc++, and the tr1 headers will be there.
长答案:错误的原因和包括两组C ++的原因是macOS/Xcode具有两个可以针对其构建的C ++标准库:一个旧的GNU libstdc++和一个新的和现代的LLVM libc++.
Long answer:The reason for your error and the 2 sets of C++ includes is that macOS/Xcode has two different C++ standard libraries you can build against: an old GNU libstdc++, and the new and modern LLVM libc++.
从macOS 10.12 Sierra开始，默认值现在为libc++，而已弃用libstdc++. libstdc++很老，v4.2.1，且早于C ++ 11(因此，tr1标头).如果您要长期使用此代码，则值得花时间使其至少符合C ++ 11(即#include <unordered_map>)
As of macOS 10.12 Sierra, the default is now libc++ and libstdc++ is deprecated. libstdc++ is quite old, v4.2.1, and predates C++11 (hence the tr1 headers). If you're going to be using this code long-term, it'd be worth the time to at least make it C++11 compliant (i.e. #include <unordered_map>)
更新:Xcode 10不再允许针对libstdc ++进行构建.更新您的代码库以使用标准的C ++ 11标头，或者如果确实没有选择，请使用Xcode 9.
Update: Xcode 10 no longer allows building against libstdc++. Either update your codebase to use standard C++11 headers, or use Xcode 9 if that's really not an option.
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