该程序初步演示了我对vector在分配内存的时候的理解。可能有误差，随着理解的改变，改代码可以被修改。
/*
功能说明：
vector的内存分配机制分析。
代码说明：
vector所管理的内存地址是连续的。程序在不断的push_back的过程中，如果当前所管理的内存不能装下新的元素的时候，程序会创建更大的地址连续的空间来保存更多的元素。
这种机制会引起大量的无用的复制和删除操作。如果vector的元素为类结构的时候，他就会有很多临时变量产生。通过复制构造函数和析构函数，可以看到这些操作。
实现方式： 限制条件或者存在的问题：
无
*/
#include <iostream>
#include <string>
#include <vector> #include <windows.h> using namespace std; class CData
{
public:
CData()
{
sequence = ;
this->remark = "default string"; cout << "CData()\t" << toString() <<"\t"<< this << endl;
} CData(int i,string &s)
{
this->sequence = i;
this->remark = s; cout << "CData(int i,string &s)\t" << toString() << "\t" << this << endl;
} CData(const CData &data)
{
this->sequence = data.sequence;
this->remark = data.remark; cout << "CData(const CData &data)\t" << toString() << "\t" << this << endl;
} CData operator = (const CData &data)
{
this->sequence = data.sequence;
this->remark = data.remark; cout << "CData operator = (const CData &data)\t" << toString() << "\t" << this << endl; return *this;
} void setSequence(const int i)
{
this->sequence = i;
} void setRemark(const string &s)
{
this->remark = s;
} string toString() const
{
char tmp[] = { };
sprintf(tmp, "[sequence:%d | remark:%s]", this->sequence, this->remark.c_str()); //此处应该有内存复制操作，所以不用担心返回后tmp数组所指向的内存被修改或者不存在的情况。
return tmp;
} ~CData()
{
cout << "~CData()\t" << this << endl;
}
protected:
private:
int sequence;
string remark;
}; int main(int argc, char **argv)
{
cout << "process begin at " << (void*)&main << endl; string str = "baby_test";
CData data1(, str);
CData data2(, str);
CData data3(, str);
CData data4(, str);
CData data5(, str);
CData data6(, str);
CData data7(, str);
CData data8(, str);
CData data9(, str);
CData data10(, str); cout << "push CData to vector" << endl;
vector<CData> vec_data;
cout << "max size of vector<CData> is " << vec_data.max_size() << endl;
cout << "size of vector<CData> is " << vec_data.size() << endl; cout << "****************vec_data.push_back(data1)" << endl;
vec_data.push_back(data1);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data2)" << endl;
vec_data.push_back(data2);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data3)" << endl;
vec_data.push_back(data3);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data4)" << endl;
vec_data.push_back(data4);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data5)" << endl;
vec_data.push_back(data5);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data6)" << endl;
vec_data.push_back(data6);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data7)" << endl;
vec_data.push_back(data7);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data8)" << endl;
vec_data.push_back(data8);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data9)" << endl;
vec_data.push_back(data9);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data10)" << endl;
vec_data.push_back(data10);
Sleep( * vec_data.size()); // 程序到此为止，日志显示的比较怪异。
// 具体来说，就是，将CData对象push到向量中的时候，程序会通过复制构造函数，创建一些临时变量。
// 创建临时变量的原因分析：这可能与vector的内存分配方式有关。vector所创建的对象的内存的地址是连续的。
// 当当前的vector所拥有内存不能装入新的元素的时候，程序会创建开辟新的地址连续的空间，并将原来地址中的元素全部复制一份，保存到新的地址中。然后在删除原来的地址中的对象。 cout << "===============show vector by iterator" << endl;
for (vector<CData>::iterator itr = vec_data.begin(); itr != vec_data.end(); itr++)
{
// 显示的地址信息，是最后一次push的时候所复制的对象的地址。
cout << "address of itr is " << &(*itr) << "\tvalue is " << itr->toString() << endl;
} cout << "===============clear vector 1" << endl;
// vector中的元素不是指针，此处的清理，会调用析构函数。
vec_data.clear(); // 根据上面的分析，再次测试。
// 本次测试是在将元素push到vector中之前，先为vector申请“足够大”的内存。
vec_data.reserve();
cout << "size of vector<CData> is " << vec_data.size() << endl;
cout << "capacity of vector<CData> is " << vec_data.capacity() << endl; cout << "****************vec_data.push_back(data1)" << endl;
vec_data.push_back(data1);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data2)" << endl;
vec_data.push_back(data2);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data3)" << endl;
vec_data.push_back(data3);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data4)" << endl;
vec_data.push_back(data4);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data5)" << endl;
vec_data.push_back(data5);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data6)" << endl;
vec_data.push_back(data6);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data7)" << endl;
vec_data.push_back(data7);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data8)" << endl;
vec_data.push_back(data8);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data9)" << endl;
vec_data.push_back(data9);
Sleep( * vec_data.size()); cout << "****************vec_data.push_back(data10)" << endl;
vec_data.push_back(data10);
Sleep( * vec_data.size()); cout << "===============show vector by iterator 2" << endl;
for (vector<CData>::iterator itr = vec_data.begin(); itr != vec_data.end(); itr++)
{
cout << "address of itr is " << &(*itr) << "\tvalue is " << itr->toString() << endl;
} // 上面的日志信息显示。vector开始已经有了足够大的地址空间来保存这10个变量，所以，他就不会再频繁创建新的内存地址和创建新对象了。
// 这样的方式，可以节省很多的系统开销。 cout << "===============clear vector 2" << endl;
// vector中的元素不是指针，此处的清理，会调用析构函数。
vec_data.clear(); cout << "======================end of process" << endl; return ;
}
程序的结果：
process begin at 00D1173A
CData(int i,string &s) [sequence:1 | remark:baby_test] 00CAFAD0
CData(int i,string &s) [sequence:2 | remark:baby_test] 00CAFAA8
CData(int i,string &s) [sequence:3 | remark:baby_test] 00CAFA80
CData(int i,string &s) [sequence:4 | remark:baby_test] 00CAFA58
CData(int i,string &s) [sequence:5 | remark:baby_test] 00CAFA30
CData(int i,string &s) [sequence:6 | remark:baby_test] 00CAFA08
CData(int i,string &s) [sequence:7 | remark:baby_test] 00CAF9E0
CData(int i,string &s) [sequence:8 | remark:baby_test] 00CAF9B8
CData(int i,string &s) [sequence:9 | remark:baby_test] 00CAF990
CData(int i,string &s) [sequence:10 | remark:baby_test] 00CAF968
push CData to vector
max size of vector<CData> is 134217727
size of vector<CData> is 0
****************vec_data.push_back(data1)
CData(const CData &data) [sequence:1 | remark:baby_test] 010485A8
****************vec_data.push_back(data2)
CData(const CData &data) [sequence:1 | remark:baby_test] 01046F60
~CData() 010485A8
CData(const CData &data) [sequence:2 | remark:baby_test] 01046F80
****************vec_data.push_back(data3)
CData(const CData &data) [sequence:1 | remark:baby_test] 0104D230
CData(const CData &data) [sequence:2 | remark:baby_test] 0104D250
~CData() 01046F60
~CData() 01046F80
CData(const CData &data) [sequence:3 | remark:baby_test] 0104D270
****************vec_data.push_back(data4)
CData(const CData &data) [sequence:1 | remark:baby_test] 0104D2C0
CData(const CData &data) [sequence:2 | remark:baby_test] 0104D2E0
CData(const CData &data) [sequence:3 | remark:baby_test] 0104D300
~CData() 0104D230
~CData() 0104D250
~CData() 0104D270
CData(const CData &data) [sequence:4 | remark:baby_test] 0104D320
****************vec_data.push_back(data5)
CData(const CData &data) [sequence:1 | remark:baby_test] 0104E430
CData(const CData &data) [sequence:2 | remark:baby_test] 0104E450
CData(const CData &data) [sequence:3 | remark:baby_test] 0104E470
CData(const CData &data) [sequence:4 | remark:baby_test] 0104E490
~CData() 0104D2C0
~CData() 0104D2E0
~CData() 0104D300
~CData() 0104D320
CData(const CData &data) [sequence:5 | remark:baby_test] 0104E4B0
****************vec_data.push_back(data6)
CData(const CData &data) [sequence:6 | remark:baby_test] 0104E4D0
****************vec_data.push_back(data7)
CData(const CData &data) [sequence:1 | remark:baby_test] 0104D230
CData(const CData &data) [sequence:2 | remark:baby_test] 0104D250
CData(const CData &data) [sequence:3 | remark:baby_test] 0104D270
CData(const CData &data) [sequence:4 | remark:baby_test] 0104D290
CData(const CData &data) [sequence:5 | remark:baby_test] 0104D2B0
CData(const CData &data) [sequence:6 | remark:baby_test] 0104D2D0
~CData() 0104E430
~CData() 0104E450
~CData() 0104E470
~CData() 0104E490
~CData() 0104E4B0
~CData() 0104E4D0
CData(const CData &data) [sequence:7 | remark:baby_test] 0104D2F0
****************vec_data.push_back(data8)
CData(const CData &data) [sequence:8 | remark:baby_test] 0104D310
****************vec_data.push_back(data9)
CData(const CData &data) [sequence:9 | remark:baby_test] 0104D330
****************vec_data.push_back(data10)
CData(const CData &data) [sequence:1 | remark:baby_test] 0104ED28
CData(const CData &data) [sequence:2 | remark:baby_test] 0104ED48
CData(const CData &data) [sequence:3 | remark:baby_test] 0104ED68
CData(const CData &data) [sequence:4 | remark:baby_test] 0104ED88
CData(const CData &data) [sequence:5 | remark:baby_test] 0104EDA8
CData(const CData &data) [sequence:6 | remark:baby_test] 0104EDC8
CData(const CData &data) [sequence:7 | remark:baby_test] 0104EDE8
CData(const CData &data) [sequence:8 | remark:baby_test] 0104EE08
CData(const CData &data) [sequence:9 | remark:baby_test] 0104EE28
~CData() 0104D230
~CData() 0104D250
~CData() 0104D270
~CData() 0104D290
~CData() 0104D2B0
~CData() 0104D2D0
~CData() 0104D2F0
~CData() 0104D310
~CData() 0104D330
CData(const CData &data) [sequence:10 | remark:baby_test] 0104EE48
===============show vector by iterator
address of itr is 0104ED28 value is [sequence:1 | remark:baby_test]
address of itr is 0104ED48 value is [sequence:2 | remark:baby_test]
address of itr is 0104ED68 value is [sequence:3 | remark:baby_test]
address of itr is 0104ED88 value is [sequence:4 | remark:baby_test]
address of itr is 0104EDA8 value is [sequence:5 | remark:baby_test]
address of itr is 0104EDC8 value is [sequence:6 | remark:baby_test]
address of itr is 0104EDE8 value is [sequence:7 | remark:baby_test]
address of itr is 0104EE08 value is [sequence:8 | remark:baby_test]
address of itr is 0104EE28 value is [sequence:9 | remark:baby_test]
address of itr is 0104EE48 value is [sequence:10 | remark:baby_test]
===============clear vector 1
~CData() 0104ED28
~CData() 0104ED48
~CData() 0104ED68
~CData() 0104ED88
~CData() 0104EDA8
~CData() 0104EDC8
~CData() 0104EDE8
~CData() 0104EE08
~CData() 0104EE28
~CData() 0104EE48
size of vector<CData> is 0
capacity of vector<CData> is 20
****************vec_data.push_back(data1)
CData(const CData &data) [sequence:1 | remark:baby_test] 0104EEF8
****************vec_data.push_back(data2)
CData(const CData &data) [sequence:2 | remark:baby_test] 0104EF18
****************vec_data.push_back(data3)
CData(const CData &data) [sequence:3 | remark:baby_test] 0104EF38
****************vec_data.push_back(data4)
CData(const CData &data) [sequence:4 | remark:baby_test] 0104EF58
****************vec_data.push_back(data5)
CData(const CData &data) [sequence:5 | remark:baby_test] 0104EF78
****************vec_data.push_back(data6)
CData(const CData &data) [sequence:6 | remark:baby_test] 0104EF98
****************vec_data.push_back(data7)
CData(const CData &data) [sequence:7 | remark:baby_test] 0104EFB8
****************vec_data.push_back(data8)
CData(const CData &data) [sequence:8 | remark:baby_test] 0104EFD8
****************vec_data.push_back(data9)
CData(const CData &data) [sequence:9 | remark:baby_test] 0104EFF8
****************vec_data.push_back(data10)
CData(const CData &data) [sequence:10 | remark:baby_test] 0104F018
===============show vector by iterator 2
address of itr is 0104EEF8 value is [sequence:1 | remark:baby_test]
address of itr is 0104EF18 value is [sequence:2 | remark:baby_test]
address of itr is 0104EF38 value is [sequence:3 | remark:baby_test]
address of itr is 0104EF58 value is [sequence:4 | remark:baby_test]
address of itr is 0104EF78 value is [sequence:5 | remark:baby_test]
address of itr is 0104EF98 value is [sequence:6 | remark:baby_test]
address of itr is 0104EFB8 value is [sequence:7 | remark:baby_test]
address of itr is 0104EFD8 value is [sequence:8 | remark:baby_test]
address of itr is 0104EFF8 value is [sequence:9 | remark:baby_test]
address of itr is 0104F018 value is [sequence:10 | remark:baby_test]
===============clear vector 2
~CData() 0104EEF8
~CData() 0104EF18
~CData() 0104EF38
~CData() 0104EF58
~CData() 0104EF78
~CData() 0104EF98
~CData() 0104EFB8
~CData() 0104EFD8
~CData() 0104EFF8
~CData() 0104F018
======================end of process
~CData() 00CAF968
~CData() 00CAF990
~CData() 00CAF9B8
~CData() 00CAF9E0
~CData() 00CAFA08
~CData() 00CAFA30
~CData() 00CAFA58
~CData() 00CAFA80
~CData() 00CAFAA8
~CData() 00CAFAD0