使用以下命令编译它时出现此错误：g++ main.cpp Vec.cpp -Wall -o main -I。
/tmp/cciqbEQJ.o: In function `main':
main.cpp:(.text+0x8b): undefined reference to `Vec<double>::Vec()'
main.cpp:(.text+0x9b): undefined reference to `Vec<double>::~Vec()'
collect2: ld returned 1 exit status
make: *** [all] Error 1
我不明白，因为我以前做过很多多源文件程序，但从未遇到过找不到构造函数的错误。编译器似乎无法将模板代码动态绑定到模板的实例化。另外，我在 .h 文件上放置了宏保护，但下面未显示。
源代码如下：
Vec.cpp
#include "Vec.h"
using namespace std;
template<class T>
Vec<T>::Vec() {
create();
}
template<class T>
Vec<T>::Vec( size_type n, const value_type& t ){
create(n,t);
}
template<class T>
Vec<T>::Vec(const Vec& v)
{
create(v.begin(), v.end());
}
template<class T>
Vec<T>::~Vec(){
uncreate();
}
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) {
iterator it = avail;
while (it != data)
alloc.destroy(--it);
alloc.deallocate(data,limit-data);
}
data = limit = avail =0;
}
template<class T> void Vec<T>::grow() {
size_type new_size = max ( 2 * (limit-data), ptrdiff_t(1));
iterator new_data = alloc.allocate(new_size);
iterator new_avail = unitialized_copy(data, avail, new_data);
uncreate();
data = new_data;
avail = new_avail;
limit = data + new_size;
}
template<class T> void Vec<T>::unchecked_append(const T& val) {
alloc.construct(avail++, val);
}
template<class T>
void Vec<T>::push_back(const T& t){
if ( avail == limit )
grow();
unchecked_append(t);
}
向量
template<class T> class Vec{
public:
typedef T* iterator;
typedef const T* const_iterator;
typedef size_t size_type;
typedef T value_type;
Vec();
Vec( size_type n, const T& t=T() );
Vec(const Vec& v);
Vec& operator=(const Vec& v);
~Vec();
void push_back(const T& t);
inline size_type size() const { return limit - data; }
inline iterator begin() {return data;}
inline const_iterator begin() const { return data; }
inline iterator end() { return limit; }
inline const_iterator end() const { return limit; }
inline T& operator[](size_type i){
return data[i];
}
const T& operator[](size_type i) const { return data[i]; }
private:
iterator data;
iterator limit;
iterator avail;
//facilities for memory allocation
allocator<T> alloc;
//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&);
};
main.cpp
int main(void) {
Vec<double> test;
}
