constexpr静态std :: array <const char =“” *，5 =“”>无法使用MSVC2013编译

时间：2019-04-03 11:53:10

标签： c++ c++11

我有此代码：

#include <array>
#include <iostream>

class ExternalGeometryExtension
{
public:
    enum Flag {
        Defining = 0,
        Frozen = 1, 
        Detached = 2,
        Missing = 3,
        Sync = 4,
        NumFlags
    };

    constexpr static std::array<const char *,NumFlags> flag2str{{ "Defining", "Frozen", "Detached","Missing", "Sync" }};
};

int main()
{
    std::cout << ExternalGeometryExtension::flag2str[ExternalGeometryExtension::Frozen] << std::endl;
    return 0;
}

它可以用以下命令进行编译： clang版本5.0.0和 gcc（Ubuntu 4.8.4-2ubuntu1〜14.04.3）4.8.4

它无法与MSVC2013一起编译。

编译错误为：

 C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2144: syntax error : 'int' should be preceded by ';' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2146: syntax error : missing ';' before identifier 'flag2str' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2838: 'array<char const *,5>' : illegal qualified name in member declaration [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2143: syntax error : missing ';' before '{' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2334: unexpected token(s) preceding '{'; skipping apparent function body [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod\Sketcher\App\ExternalGeometryExtension.cpp(36): error C2143: syntax error : missing ';' before 'std::array<const char *,0x05>' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod\Sketcher\App\ExternalGeometryExtension.cpp(36): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod\Sketcher\App\ExternalGeometryExtension.cpp(36): error C2039: 'flag2str' : is not a member of 'Sketcher::ExternalGeometryExtension' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         c:\projects\freecad\src\mod\sketcher\app\ExternalGeometryExtension.h(47): error C2144: syntax error : 'int' should be preceded by ';' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         c:\projects\freecad\src\mod\sketcher\app\ExternalGeometryExtension.h(47): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         c:\projects\freecad\src\mod\sketcher\app\ExternalGeometryExtension.h(47): error C2146: syntax error : missing ';' before identifier 'flag2str' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         c:\projects\freecad\src\mod\sketcher\app\ExternalGeometryExtension.h(47): error C2838: 'array<char const *,5>' : illegal qualified name in member declaration [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         c:\projects\freecad\src\mod\sketcher\app\ExternalGeometryExtension.h(47): error C2143: syntax error : missing ';' before '{' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         c:\projects\freecad\src\mod\sketcher\app\ExternalGeometryExtension.h(47): error C2334: unexpected token(s) preceding '{'; skipping apparent function body [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2144: syntax error : 'int' should be preceded by ';' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2146: syntax error : missing ';' before identifier 'flag2str' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2838: 'array<char const *,5>' : illegal qualified name in member declaration [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2143: syntax error : missing ';' before '{' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod/Sketcher/App/ExternalGeometryExtension.h(47): error C2334: unexpected token(s) preceding '{'; skipping apparent function body [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]
         C:\projects\freecad\src\Mod\Sketcher\App\ExternalGeometryExtensionPyImp.cpp(67): error C2039: 'flag2str' : is not a member of 'Sketcher::ExternalGeometryExtension' [C:\projects\freecad\build\src\Mod\Sketcher\App\Sketcher.vcxproj]

完整的编译器输出here

我的问题是： 我做错了什么？为什么不使用MSVC2013进行编译？

是否可以做一些使该代码与MSVC2013一起使用而又不会在其他编译器中破坏它的事情？

编辑：我已经更改了代码，以使它是Toby Speight基于Diodacus的良好猜测所要求的最小，完整和可验证的示例。我无法生成该特定代码的错误输出，因为我没有MSVC2003的副本。我使用提供Windows支持的开源FreeCAD。我使用Linux。无论如何，输出中的错误都与我显示的代码相对应。这是集成之前AppVeyor测试的输出。该代码通过了Linux CI的罚款。我将尽量利用这个问题，希望对其他人有用。

编辑2：我已经意识到双括号初始化引起了一些注意。来自cppreference中的示例：

  CWG 1270修订版之前，C ++ 11中需要

双括号   （修订后的C ++ 11中以及C ++ 14及更高版本中不需要）

没有双括号，gcc 4.8会失败。

2 个答案:

答案 0 :(得分：8)

根据此microsoft devblog，constexpr是VS 2013不支持的C ++ 11核心语言功能之一。“ 2013年11月CTP”仅部分支持它。 / p>

答案 1 :(得分：-1)

好吧，所讨论的代码确实可以使用C ++ 17选项进行编译：

def encode(s):
    return ''.join('&{};'.format(codepoint2name.get(i, '#{}'.format(i))) for i in map(ord, s))

并且无需在类外重新声明静态变量。

@Abdullah Tahiri请使用C ++ 11构造（如问题标签所述），或使用C ++ 17获得所有功能。但是我担心MSVC的代码可能有问题。您是否有任何特殊原因无法在Windows上使用GCC或CLang？

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