iphone编译器继承的模板基类与传递通过类型不扩展的时间（只是看） [英] iphone compiler inherited templated base classes with passed through type not being expanded in time (just look)

问题描述

尝试此操作：

    template <typename T>
    class Base
        {
        public:
            int someBaseMember;
        };

    template <typename T>
    class Test: public Base<T>
    {
    public:
        void testFunc()
        {
            someBaseMember = 0;
        }
    };

在vc ++和psp编译器（以及遇到的任何其他编译器） ，用iphone编译器（设备，gcc 4.2我想，与-fpermissive标志设置）我得到一个错误说
'someBaseMember没有定义'
在
'someBaseMember = 0 ;'
行

In vc++ and the psp compiler (and any other compiler I've encountered) the above will work fine, with the iphone compiler (for device, gcc 4.2 I think, with the -fpermissive flag set) I get an error saying 'someBaseMember is not defined' on the 'someBaseMember = 0;' line

iphone编译器似乎比其他编译器更快地'解析'模板化的代码，甚至没有语法检查他们，直到你实际CALL函数，或实例化一个实例。）

The iphone compiler seems to be 'parsing' templated code a lot sooner than other compilers do, (from what I can tell, most others don't even syntax check them until you actually CALL the function, or instantiate an instance.)

从我可以告诉它很快，它的解析它没有

From what I can tell its parsing it so soon that it hasn't even parsed the base class yet :S its like it doesn't exist.

任何想法？

推荐答案

您得到的错误是正确的（其他编译器不应该接受代码，并且这样错误）;变量 someBaseMember 取决于 Base< T> 的模板实例化， ，因此编译器在尝试独立于模板参数进行解析时是正确的。

The error that you are getting is correct (the other compilers should not accept the code and are doing so erroneously); the variable someBaseMember depends on the template instantation of Base<T>, but this dependence has not been expressed in your usage, and hence the compiler is correct in attempting to resolve it independently of the template parameter.

您可以通过使此依赖性显式来解决此问题，从而强制编译器解析该变量使用模板实例化。您可以使用以下任意一种：

You can resolve this problem by making this dependence explicit, thereby forcing the compiler to resolve the variable using the template instantation. You can use either of the following:


this-> someBaseMember = 0;


或


Base< T> :: someBaseMember = 0;


上述两种情况都会导致您想要的解析机制。

Either of the above should result in the resolution mechanism you want.

EDIT

您可能希望看到C ++ FAQ Lite的相关部分：

http://www.parashift.com/c++-faq-lite/templates.html#faq- 35.19

http ：//www.parashift.com/c++-faq-lite/templates.html#faq-35.18

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