c++ - 模糊的C++编译错误

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任何人都可以对此提出建议：

In file included from recorders/r5000channel.h:13:0,
             from recorders/r5000channel.cpp:11:
recorders/dtvchannel.h:53:18: warning: ‘virtual bool DTVChannel::Tune(const IPTVTuningData&)’ was hidden [-Woverloaded-virtual]
 virtual bool Tune(const IPTVTuningData&) { return false; }
              ^
In file included from recorders/r5000channel.cpp:11:0:
recorders/r5000channel.h:29:18: warning:   by ‘virtual bool R5000Channel::Tune(const DTVMultiplex&, QString)’ [-Woverloaded-virtual]
 virtual bool Tune(const DTVMultiplex &/*tuning*/, QString /*inputname*/)
              ^
In file included from recorders/r5000channel.h:13:0,
             from recorders/r5000channel.cpp:11:
recorders/dtvchannel.h:65:18: warning: ‘virtual bool DTVChannel::Tune(const QString&, int)’ was hidden [-Woverloaded-virtual]
 virtual bool Tune(const QString &freqid, int finetune)
              ^
In file included from recorders/r5000channel.cpp:11:0:
recorders/r5000channel.h:29:18: warning:   by ‘virtual bool R5000Channel::Tune(const DTVMultiplex&, QString)’ [-Woverloaded-virtual]
 virtual bool Tune(const DTVMultiplex &/*tuning*/, QString /*inputname*/)
              ^
In file included from recorders/r5000channel.h:13:0,
             from recorders/r5000channel.cpp:11:
recorders/dtvchannel.h:71:18: warning: ‘virtual bool DTVChannel::Tune(uint64_t, QString)’ was hidden [-Woverloaded-virtual]
 virtual bool Tune(uint64_t frequency, QString inputname)
              ^
In file included from recorders/r5000channel.cpp:11:0:
recorders/r5000channel.h:29:18: warning:   by ‘virtual bool R5000Channel::Tune(const DTVMultiplex&, QString)’ [-Woverloaded-virtual]
 virtual bool Tune(const DTVMultiplex &/*tuning*/, QString /*inputname*/)

r5000channel.h-https://pastee.org/rjajf

r5000channel.cpp-https://pastee.org/qangy

最佳答案

请注意，这不是错误，而是警告。看来您的基类包含名为virtual的Tune函数的重载版本：当您覆盖其中的一个时，使用派生对象时基中的所有版本都被隐藏。通常，这是无意的，处理重载的virtual函数的通常方法是使virtual函数protected，从public转发（可能是inline）函数委派给他们。参见例如virtual中的std::num_get<...>函数。

避免隐藏的另一种方法是提供using-声明以及virtual函数的替代。就个人而言，我更喜欢转发方法。

显示的警告实际上来自头文件。这意味着您正在使用的库是草率的，或者您创建的草率基类有些草率。

这是显示问题的SSCCE，并在注释中给出了解决方法：

struct base
{
    virtual void foo(int) {}
    virtual void foo(bool) {}
};

struct derived: base
{
    virtual void foo(int) {}
    // add this: using base::foo;
};

int main()
{
}

当我用上面的代码编译时，得到以下消息（缩写为仅显示编译器版本和警告）：

$ g++ -v -c -Woverloaded-virtual overloaded-virtual.cpp
[...]
GNU C++ (GCC) version 4.9.0 20131031 (experimental) (x86_64-apple-darwin13.0.0)
    compiled by GNU C version 4.9.0 20131102 (experimental), GMP version 5.0.5, MPFR version 3.1.1, MPC version 1.0.1
[...]
overloaded-virtual.cpp:4:22: warning: ‘virtual void base::foo(bool)’ was hidden [-Woverloaded-virtual]
         virtual void foo(bool) {}
                      ^
overloaded-virtual.cpp:9:22: warning:   by ‘virtual void derived::foo(int)’ [-Woverloaded-virtual]
         virtual void foo(int) {}
                      ^

添加评论时，警告消失（如预期）。

关于c++ - 模糊的C++编译错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/20206370/