std :: function没有成员名为'target' [英] std::function has no member named 'target'

问题描述

我试图存储唯一的函数指针列表。纯粹的指针的一个明显的包装看起来 std :: function 。

I am trying to store list of unique function pointers. An obvious wrapper to pure pointers seem std::function.

事实证明， std :: function s 无法比较。

然后，对原始指针的简单比较应该工作，对吧？也许，但我得到以下错误以下代码。我的编译器是gcc 4.7.2。这是在2012年没有实现的东西吗？

Then a simple comparison of the raw pointers should work, right? Maybe, but I am getting the following error for the following code. My compiler is gcc 4.7.2. Is this something that was not implemented back in 2012?

    std::function<void(bool)> f;
    void(*p)(bool) = f.target<void(*)(bool)>();

错误：'class std :: function'目标'

error: 'class std::function' has no member named 'target'

---

这里是相关的，除了标题：

---

Here is the relevant except from the header:

#ifdef __GXX_RTTI
      // [3.7.2.5] function target access
      /**
       *  @brief Determine the type of the target of this function object
       *  wrapper.
       *
       *  @returns the type identifier of the target function object, or
       *  @c typeid(void) if @c !(bool)*this.
       *
       *  This function will not throw an %exception.
       */
      const type_info& target_type() const noexcept;

      /**
       *  @brief Access the stored target function object.
       *
       *  @return Returns a pointer to the stored target function object,
       *  if @c typeid(Functor).equals(target_type()); otherwise, a NULL
       *  pointer.
       *
       * This function will not throw an %exception.
       */
      template<typename _Functor>       _Functor* target() noexcept;

      /// @overload
      template<typename _Functor> const _Functor* target() const noexcept;
#endif

推荐答案

好。 RTTI需要在编译器标志中启用。
我在编译器标志中有 -fno-rtti 。

I had this problem as well. RTTI needs to be enabled in the compiler flags. I had -fno-rtti in the compiler flags.

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