C ++ 11填充胶 [英] C++11 Polyfills

问题描述

我正在启动一个新项目，该项目的目标是MSVC，GCC (latest)，GCC 4.3 ARM等.我们构建的waf构建系统具有对编译器的C++11功能检测.

I am starting a new project that will be targeting MSVC, GCC (latest), GCC 4.3 ARM and more. The waf build system we have built has C++11 feature detection of the compiler.

我现在拥有针对C++11的编译器中所有功能的预处理器宏，例如#ifdef WAF_FEATURE_CXX_STRONGLY_TYPED_ENUMS.因此，我可以为编译器支持的内容编译不同的代码.由于GCC几乎支持它，因此MSVC甚至都没有关闭(即使使用MSVC 11)

I now have preprocessor macros for all features in compiler that I am targeting for C++11, for example #ifdef WAF_FEATURE_CXX_STRONGLY_TYPED_ENUMS. I can therefore compile different code for what the compiler supports. As GCC nearly supports it all be MSVC isn't even close (even with MSVC 11)

这使我想到了Web开发polyfills-如果该功能不可用，请使用可用的功能集将其实现.

This got me thinking about web development polyfills - if the feature isn't available implement it with the feature set available.

这没有像C++11那样简单的Web开发polyfill，但是如果编译器不支持的话，有什么我可以简单地用C ++ 03实现的东西吗?

This is no way near as simple as web development polyfills as for C++11 but is there anything that I can simply implement with C++03 if the compiler doesn't support it?

这归结为以下事实:我想在我的公共API中使用强类型的枚举器，但作用域MyClass::MyEnumerator::EnumValue看起来更像C++03中的MyClass::EnumValue.无论如何，我可以很容易地在C++03中发生同样的事情:

This boils down to the fact that I want to use strongly typed enumerators in my public API but the scoping MyClass::MyEnumerator::EnumValue will look more like MyClass::EnumValue in C++03. Is there anyway I can get the same to occur in C++03 easily:

class MyClass {
    public:
#ifdef WAF_FEATURE_CXX_STRONGLY_TYPED_ENUMS
        enum class MyEnumerator : unsigned int {
#else
        enum MyEnumerator {
#endif
             EnumValue = 0
        }
    void method(MyEnumerator e);
}

MyClass mc = new MyClass();
mc.method(MyClass::MyEnumerator::EnumValue) // C++11
mc.method(MyClass::EnumValue)               // C++03 :(

推荐答案

这是您需要做的(我对指针和非指针访问进行了其他琐碎的修复). 基本上，这就是@demi所说的.我必须做一个虚拟的枚举名称.这适用于g ++-4.7.

This is what you'll need to do (I made other trivial fixes about pointers and non-pointer access). Bsically, it's what @demi said. I had to make a dummy enum name. This works in g++-4.7.

class MyClass {
    public:
#if __cplusplus > 201000
        enum class MyEnumerator : unsigned int {
             EnumValue = 0
        };
    void method(MyEnumerator e) {}
#else
        class MyEnumerator {
        public:
          enum Dummy {
             EnumValue = 0
          };
        };
    void method(MyEnumerator::Dummy e) {}
#endif
};

int main() {
    MyClass mc;
    mc.method(MyClass::MyEnumerator::EnumValue); // C++11 or C++03
}

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