C++ 的大部分STL容器类型不会随着生命周期的结束而自动释放内存，接下来将依次对其说明：

1. vector 类型

经测试，直到C++11的vector类型，用clear或者erase都无法释放内存，只有显示调用swap：

std::vector<T>.swap(t_value);

才能释放。

vector析构时会释放内存空间。

如下例：

void testVectorMemory()
{
	std::string str;
	str.append(1024, 'c');
	sleep(5);
	std::cout << "Before add vector: " << getVirtualMemory() << std::endl;

	std::vector<std::string> testVec;
	for (size_t i = 0; i<100000; i++)
	{
		testVec.push_back(str);
	}
	std::cout << "After add vector: " << getVirtualMemory() << std::endl;
	sleep(5);
	std::vector<std::string>::iterator iter = testVec.begin();
	for (; iter!=testVec.end();)
	{
		iter = testVec.erase(iter);
	}
	std::cout << "After erase vector: " << getVirtualMemory() << std::endl;
	sleep(5);
}
int main(int argc, char *argv[])
{
	std::cout << "Before test: " << getVirtualMemory() << std::endl;
	testVectorMemory();
	sleep(10);
	std::cout << "After test: " << getVirtualMemory() << std::endl;

	sleep(100);
	std::cout << "After test, after 100 seconds: " << getVirtualMemory() << std::endl;
	return 0;
}

测试结果：

Before test: 4088
Before add vector: 4096
After add vector: 4620
After erase vector: 4624
After test: 4112
After test, after 100 seconds: 4116

2. map类型

经测试，map分配的空间无法被释放，无论是erase, swap，就算作为局部变量，析构后也不释放 

测试代码：

void testMapMemory()
{
	std::string str;
	str.append(1024, 'c');
	sleep(5);
	std::cout << "Before add map: " << getVirtualMemory() << std::endl;

	std::map<int, std::string> tempMap;
	for (size_t i = 0; i<100000; i++)
	{
		tempMap[i] = str;
	}
	std::cout << "After add map: " << getVirtualMemory() << std::endl;
	sleep(5);
	std::map<int, std::string>::iterator iter = tempMap.begin();
	for (; iter!=tempMap.end();)
	{
		iter = tempMap.erase(iter);
	}
	std::cout << "After erase map: " << getVirtualMemory() << std::endl;
	sleep(5);
	std::map<int, std::string>().swap(tempMap);
	std::cout << "After swap map: " << getVirtualMemory() << std::endl;
	sleep(5);
}
int main(int argc, char *argv[])
{
	std::cout << "Before test: " << getVirtualMemory() << std::endl;
	testMapMemory();
	sleep(10);
	std::cout << "After test: " << getVirtualMemory() << std::endl;

	sleep(100);
	std::cout << "After test, after 100 seconds: " << getVirtualMemory() << std::endl;
	return 0;
}

测试结果：

Before test: 4096
Before add map: 4104
After add map: 7144
After erase map: 7148
After swap map: 7152
After test: 7156
After test, after 100 seconds: 7160

3. queue类型

经测试，pop方法只是删除数据，并未释放内存。swap方法或者析构只释放了部分内存。

代码：

void testQueueMemory()
{
	std::string str;
	str.append(1024, 'c');
	sleep(5);
	std::cout << "Before add queue: " << getVirtualMemory() << std::endl;

	//. test basic type
	std::queue<std::string> basicQueue;
	for (size_t i = 0; i<100000; i++)
	{
		basicQueue.push(str);
	}
	std::cout << "After add queue: " << getVirtualMemory() << std::endl;
	sleep(5);
	while(!basicQueue.empty())
	{
		basicQueue.pop();
	}
	std::cout << "After pop queue: " << getVirtualMemory() << std::endl;
	sleep(5);
	std::queue<std::string>().swap(basicQueue);
	std::cout << "After swap queue: " << getVirtualMemory() << std::endl;
	sleep(5);
}

int main(int argc, char *argv[])
{
	std::cout << "Before test: " << getVirtualMemory() << std::endl;
	testQueueMemory();
	sleep(10);
	std::cout << "After test: " << getVirtualMemory() << std::endl;

	sleep(100);
	std::cout << "After test, after 100 seconds: " << getVirtualMemory() << std::endl;
	return 0;
}

测试结果：

Before test: 4096
Before add queue: 4104
After add queue: 4504
After pop queue: 4508
After swap queue: 4232
After test: 4236
After test, after 100 seconds: 4240

4. deque类型

deque类型与queue类型唯一的区别是：

deque在使用pop后会释放一部分内存

代码：

void testDequeMemory()
{
	std::string str;
	str.append(1024, 'c');
	sleep(5);
	std::cout << "Before add queue: " << getVirtualMemory() << std::endl;

	//. test basic type
	std::deque<std::string> basicQueue;
	for (size_t i = 0; i<100000; i++)
	{
		basicQueue.push_back(str);
	}
	std::cout << "After add queue: " << getVirtualMemory() << std::endl;
	sleep(5);
	while(!basicQueue.empty())
	{
		basicQueue.pop_back();
	}
	std::cout << "After pop queue: " << getVirtualMemory() << std::endl;
	sleep(5);
}

int main(int argc, char *argv[])
{
	std::cout << "Before test: " << getVirtualMemory() << std::endl;
	testDequeMemory();
	sleep(10);
	std::cout << "After test: " << getVirtualMemory() << std::endl;

	sleep(100);
	std::cout << "After test, after 100 seconds: " << getVirtualMemory() << std::endl;
	return 0;
}

测试结果：

Before test: 4096
Before add queue: 4104
After add queue: 4504
After pop queue: 4340
After test: 4232
After test, after 100 seconds: 4236