Question

编译这个简单的代码时出现错误，如果我删除了noexcept，我就不会收到错误：

#include<vector>
#include<string>
class Foo
{
public:

protected:
   Foo(Foo&&) noexcept = default;
   Foo& operator=(Foo&&) noexcept = default;

   Foo()
   {
   }

private:

   std::vector<std::string> vectorFoo_;
};

这是我得到的错误，我理解它是在异常规范的实例化中，但是我怀疑std :: string是不是没有移动构造，...第一个错误让我觉得有一个bug。

包含来自的文件 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4： /usr/local/bin/../lib/c++/v1/vector:575:67：错误：没有成员命名＆＃39;值＆＃39;在＆＃39; std :: __ 1 :: is_nothrow_move_constructible，std :: __ 1 :: allocator＆gt; ＆GT; ＆GT;＆＃39; NOEXCEPT （is_nothrow_move_constructible ::值）; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^包括在内 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4：在/usr/local/bin/../lib/c++/v1/vector:264中包含的文件中： /usr/local/bin/../lib/c++/v1/__config:325:34：注意：扩展自宏＆＃39; NOEXCEPT ＆＃39; define NOEXCEPT （x）noexcept（x） ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中： /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29：注意：在实例化＆＃39; vector＆＃39;的异常规范中这里请求std :: vector vectorFoo_; ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4：在/usr/local/bin/../lib/c++/v1/vector:265中包含的文件中：在文件中包括在/usr/local/bin/../lib/c++/v1/__bit_reference:15：在文件中包含在/usr/local/bin/../lib/c++/v1/algorithm:624中： /usr/local/bin/../lib/c++/v1/type_traits:2676:53：注意：在模板类的实例化＆＃39; std :: __ 1 :: add_rvalue_reference，std :: __ 1 :: allocator＆gt; ＆GT; ＆GT;＆＃39; 这里要求：public is_nothrow_constructible＆lt; _Tp，typename add_rvalue_reference＆lt; Tp＆gt; :: type＆gt; ^在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4： /usr/local/bin/../lib/c++/v1/vector:575:20：注意：在实例化中模板类＆＃39; std :: _1 :: is_nothrow_move_constructible，std :: __ 1 :: allocator＆gt; ＆GT; ＆GT;＆＃39; 这里要求 NOEXCEPT （is_nothrow_move_constructible ::值）; ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4：在/usr/local/bin/../lib/c++/v1/vector:264中包含的文件中： /usr/local/bin/../lib/c++/v1/__config:325:34：注意：扩展自宏＆＃39; NOEXCEPT ＆＃39; define NOEXCEPT （x）noexcept（x） ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中： /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29：注意：在实例化＆＃39; vector＆＃39;的异常规范中这里请求std :: vector vectorFoo_; ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4： /usr/local/bin/../lib/c++/v1/vector:582:58：错误：没有成员命名＆＃39;值＆＃39;在＆＃39; std :: __ 1 :: is_nothrow_move_assignable，std :: __ 1 :: allocator＆gt; ＆GT; ＆GT;＆＃39; is_nothrow_move_assignable ::值）; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4：在/usr/local/bin/../lib/c++/v1/vector:264中包含的文件中： /usr/local/bin/../lib/c++/v1/__config:325:34：注意：扩展自宏＆＃39; NOEXCEPT ＆＃39; define NOEXCEPT （x）noexcept（x） ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中： /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29：注意：在＆＃39; operator =＆＃39;的异常规范实例化中这里请求std :: vector vectorFoo_; ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4：在/usr/local/bin/../lib/c++/v1/vector:265中包含的文件中：在文件中包括在/usr/local/bin/../lib/c++/v1/__bit_reference:15：在文件中包含在/usr/local/bin/../lib/c++/v1/algorithm:624中： /usr/local/bin/../lib/c++/v1/type_traits:2760:45：注意：在模板类的实例化＆＃39; std :: __ 1 :: add_lvalue_reference，std :: __ 1 :: allocator＆gt; ＆GT; ＆GT;＆＃39; 这里要求：public is_nothrow_assignableTp＆gt; :: type， ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4： /usr/local/bin/../lib/c++/v1/vector:582:14：注意：在实例化中模板类＆＃39; std :: _ 1 :: is_nothrow_move_assignable，std :: __ 1 :: allocator＆gt; ＆GT; ＆GT;＆＃39; 这里要求 is_nothrow_move_assignable ::值）; ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4：在/usr/local/bin/../lib/c++/v1/vector:264中包含的文件中： /usr/local/bin/../lib/c++/v1/__config:325:34：注意：扩展自宏＆＃39; NOEXCEPT ＆＃39; define NOEXCEPT （x）noexcept（x） ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中： /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29：注意：在＆＃39; operator =＆＃39;的异常规范实例化中这里请求std :: vector vectorFoo_; ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4：在/usr/local/bin/../lib/c++/v1/vector:265中包含的文件中：在文件中包括在/usr/local/bin/../lib/c++/v1/__bit_reference:15：在文件中包含在/usr/local/bin/../lib/c++/v1/algorithm:624中： /usr/local/bin/../lib/c++/v1/type_traits:2676:53：注意：在模板类的实例化＆＃39; std :: __ 1 :: add_rvalue_reference，std :: __ 1 :: allocator＆gt; ＆GT; ＆GT;＆＃39; 这里要求：public is_nothrow_constructible＆lt; _Tp，typename add_rvalue_reference＆lt; Tp＆gt; :: type＆gt; ^在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4： /usr/local/bin/../lib/c++/v1/vector:575:20：注意：在实例化中模板类＆＃39; std :: _1 :: is_nothrow_move_constructible，std :: __ 1 :: allocator＆gt; ＆GT; ＆GT;＆＃39; 这里要求 NOEXCEPT （is_nothrow_move_constructible ::值）; ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中：在包含的文件中 /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:4：在/usr/local/bin/../lib/c++/v1/vector:264中包含的文件中： /usr/local/bin/../lib/c++/v1/__config:325:34：注意：扩展自宏＆＃39; NOEXCEPT ＆＃39; define NOEXCEPT （x）noexcept（x） ^在/Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.cpp:1中包含的文件中： /Users/Mani/Development/Projects/flowOfLife/Graphics/Graphics/TestCompileError.h:29:29：注意：在实例化＆＃39; vector＆＃39;的异常规范中这里请求std :: vector vectorFoo _;

我的编译器是从树顶部开始的。我做错了什么？

由于

更新 The error on Coliru。如果我没有指定libc ++，而是使用stdlibc ++，它就会编译。它开始看起来很像libc ++中的一个bug。

Answer 1

代码很好。（有趣的是，libc ++也是如此）

这是铿锵声中的一个错误;事实上，最近版本的clang在尝试编译此代码时崩溃。

目前正在测试在clang中修复此问题的修补程序，它将成为3.4版本的一部分。如果您不能等待那么久，那么如果您愿意从源代码构建它，那么您应该能够“很快就能获得”固定版本的clang。

感谢Nuanti的Alp追踪clang bug。

Answer 2

我的第一个假设是，这可能是因为std::string的移动赋值运算符不是noexcept（~~需要检查~~见下文）。

至少，clang和gcc似乎更喜欢这个：

Bar& operator = (Bar&&) 
     noexcept(
         noexcept(std::declval<std::string>() = std::string())
     ) = default;

现在，关于Foo clang和gcc不太同意，但这里的 Clang live on coliru

情节扭曲

更多值得深思：标准似乎明确地将std :: string的赋值运算符（以及移动构造函数）指定为noexcept：§21.4.2

libc ++实例化异常规范的向量和字符串编译简单代码时出错

2 个答案:

情节扭曲