Question

我正在尝试实现我自己的vector类作为Accelerated C ++一书的练习，但是我遇到了这些错误，我无法弄清楚如何修复它们：

C：\ MinGW \ bin .. \ lib \ gcc \ mingw32 \ 3.4.2 ........ \ include \ c ++ \ 3.4.2 \ bits \ allocator.h ||对vec的未定义引用::创建（）'|

::〜VEC（）] +×43）：C：\ MinGW的\ BIN .. \ lib中\ GCC \的mingw32 \ 3.4.2 ........ \包括\ C ++ \ 3.4.2 \位\ allocator.h ||对`vec :: uncreate（）'|

的未定义引用

我正在使用code :: blocks，两个文件都在同一个项目中，所以我很确定这不是一个链接问题。

这是vec.h文件

#ifndef VEC_H
#define VEC_H

#include <cstddef>
#include <memory>

template <class T> class vec{
public:
    typedef T* iterator;
    typedef const T* const_iterator;
    typedef size_t size_type;
    typedef T value_type;

    vec(){
        create();
    }

    explicit vec(size_type n, const T& val = T()){
        create(n,val);
    }

    vec(const vec& v){
        create(v.begin(), v.end());
    }

    ~vec(){
        uncreate();
    }

    size_type size() const{
        return avail - data;
    }

    T& operator[](size_type i){
        return data[i];
    }

    const T& operator[](size_type i) const{
        return data[i];
    }

    vec& operator = (const vec&);

    void push_back(const T& t){
        if(avail == limit)
            grow();
        unchecked_append(t);
    }

    iterator begin(){ return data; }
    const_iterator begin() const{ return data; }

    iterator end(){ return avail; }
    const_iterator end() const{ return avail; }

private:
    iterator data; //first element
    iterator avail;//one past the last available element
    iterator limit;//one past the total allocated memory

    //facilities for memory allocation

    std::allocator<T> alloc; //object to handle memory allocation

    //allocate and initialize the underlying array
    void create();
    void create(size_type, const T&);
    void create(const_iterator, const_iterator);

    //destroy the elements in the array and free the memory
    void uncreate();

    //support functions for push_back
    void grow();
    void unchecked_append(const T&);
};

#endif // VEC_H

和vec.cpp文件

#include "vec.h"

template <class T> vec<T>& vec<T>::operator=(const vec& rhs){
    //check for self-assignment
    if(&rhs != this){
        //free the array in the left-hand side
        uncreate();

        //copy elements from the right-hand to the left-hand side
        create(rhs.begin(), rhs.end());
    }

    return *this;
}

template <class T> void vec<T>::create(){
    data = avail = limit = 0;
}

template <class T> void vec<T>::create(size_type n, const T& val){
    data = alloc.allocate(n);
    limit = avail = data+n;
    uninitialized_fill(data, limit, val);
}

template <class T> void vec<T>::create(const_iterator i, const_iterator j){
    data = alloc.allocate(j-i);
    limit = avail = uninitialized_copy(i, j, data);
}

template <class T> void vec<T>::uncreate(){
    if(data){
        //destroy in reverse order the objects that were constructed
        iterator it = avail;
        while(it != data)
            destroy(--it);

        //return all the space that was allocated
        alloc.deallocate(data, limit-data);
    }

    data = limit = avail = 0;
}

template <class T> void vec<T>::grow(){
    //when growing, allocate twice as much space as currently in use
    size_type new_size = max(2*(limit-data), ptrdiff_t(1));

    //allocate new space and copy existing elements to the new space
    iterator new_data  = alloc.allocate(new_size);
    iterator new_avail = uninitialized_copy(data, avail, new_data);

    //return the old space
    uncreate();

    //reset pointers to point to the newly allocated space
    data  = new_data;
    avail = new_avail;
    limit = data + new_size;
}

//assumes avail points to allocated, but uninitialized space
template <class T> void vec<T>::unchecked_append(const T& val){
    alloc.construct(avail++, val);
}

我做错了什么？

Answer 1

由于您的类是模板，您需要将实现放入头文件中，而不是放在.cpp文件中，因为编译期间编译器需要完整的类定义。

Answer 2

必须在使用它们的每个翻译单元中定义模板;通过将函数定义放入源文件中，它们只在一个单元中定义，如果您尝试在另一个单元中使用它们，则会出错。

在类定义之后将函数定义移动到标题中。

试图实现我自己的矢量类，不断收到“未定义的引用”错误

2 个答案: