C ++指针和堆释放

问题描述

我刚开始接触C ++堆内存管理（来自JS / C＃GC管理的世界），并且想知道为什么这样做有效（！）：

此：

 for (int i{5}; i > 0; --i)
    {
        keepMakingMemoryLeak();
    }
    _CrtDumpMemoryLeaks();

调用此：

void keepMakingMemoryLeak()
{
    std::vector<std::string>* ptrToMyArray = new std::vector<std::string>;

    ptrToMyArray->push_back("John");
    ptrToMyArray->push_back("Jane");
    ptrToMyArray->push_back("Jack");

    remmotelyModifVector(ptrToMyArray);


    std::cout << "The array is: \n "; std::cout.flush();
    for (unsigned int i = 0; i < ptrToMyArray->size(); i++)
    {
        std::cout << "index: \t" << i << " is \t" << ptrToMyArray->at(i) << "\n";
    }
    std::cout << "Capacity is Now" << ptrToMyArray->capacity() << "\n";
    std::cout << "Size is Now" << ptrToMyArray->size() << "\n";

    for (unsigned int i = 0; i < ptrToMyArray->size(); i++)
    {
        if (ptrToMyArray->at(i) == "") {
            std::cout << "index: \t" << i << " exists \t" << " but is empty (zero length string) \n";
        }
    }

    delete ptrToMyArray;
}


void remmotelyModifVector(std::vector<std::string>* someArray)
{
    someArray->at(1).erase();
    someArray->shrink_to_fit();

}

上面的代码按照您的想法执行-调用keepMakingMemoryLeak() 4次，每次将std::vector分配给堆，分配一些基本字符串，将指针传递给另一个函数，该函数索引[1]，然后控制权返回给调用者keepMakingMemoryLeak()，以将向量的内容转储到cout，该过程按预期工作。（现在索引1 ==零长度字符串？还是null？）。最后，keepMakingMemoryLeak()调用delete ptrToMyArray;，然后重复循环。

使用MS内存泄漏_CrtDumpMemoryLeaks();，我得到了没有泄漏的报告-这不是我所期望的。当然，仅删除指向向量的指针就意味着向量本身（以及它的std::string元素？）仍在堆中吗？

如果我注释掉delete ptrToMyArray;，那么我这样做会得到内存泄漏报告：

Detected memory leaks!
Dumping objects ->
{308} normal block at 0x01153540,8 bytes long.
 Data: <T.      > 54 2E 15 01 00 00 00 00 
{307} normal block at 0x0114E3F0,8 bytes long.
 Data: <8.      > 38 2E 15 01 00 00 00 00 
{306} normal block at 0x0114F5E0,8 bytes long.
 Data: <p.      > 70 2E 15 01 00 00 00 00 
{305} normal block at 0x01152E38,84 bytes long.
 Data: <    John        > F0 E3 14 01 4A 6F 68 6E 00 CC CC CC CC CC CC CC 
{296} normal block at 0x0114F3B0,8 bytes long.
 Data: <,> E8 2C 15 01 00 00 00 00 
{295} normal block at 0x01152CE8,16 bytes long.
 Data: <    8.   .   .  > B0 F3 14 01 38 2E 15 01 8C 2E 15 01 8C 2E 15 01 
{282} normal block at 0x0114F848,8 bytes long.
 Data: <l-      > 6C 2D 15 01 00 00 00 00 
{281} normal block at 0x0114F618,8 bytes long.
 Data: <P-      > 50 2D 15 01 00 00 00 00 
{280} normal block at 0x0114F538,8 bytes long.
 Data: < -      > 88 2D 15 01 00 00 00 00 
{279} normal block at 0x01152D50,84 bytes long.
 Data: <    John        > 18 F6 14 01 4A 6F 68 6E 00 CC CC CC CC CC CC CC 
{270} normal block at 0x0114F298,> 00 2C 15 01 00 00 00 00 
{269} normal block at 0x01152C00,16 bytes long.
 Data: <    P-   -   -  > 98 F2 14 01 50 2D 15 01 A4 2D 15 01 A4 2D 15 01 
{256} normal block at 0x0114F260,> 84 2C 15 01 00 00 00 00 
{255} normal block at 0x0114F570,8 bytes long.
 Data: <h,> 68 2C 15 01 00 00 00 00 
{254} normal block at 0x0114F3E8,> A0 2C 15 01 00 00 00 00 
{253} normal block at 0x01152C68,84 bytes long.
 Data: <p   John        > 70 F5 14 01 4A 6F 68 6E 00 CC CC CC CC CC CC CC 
{244} normal block at 0x0114F1F0,8 bytes long.
 Data: < '      > 10 27 15 01 00 00 00 00 
{243} normal block at 0x01152710,16 bytes long.
 Data: <    h,> F0 F1 14 01 68 2C 15 01 BC 2C 15 01 BC 2C 15 01 
{230} normal block at 0x0114F308,8 bytes long.
 Data: < '      > 94 27 15 01 00 00 00 00 
{229} normal block at 0x0114F768,8 bytes long.

这很奇怪。我显然在这里遗漏了一些东西，但是研究一下并不能告诉我为什么盲目删除指针是可以的。

干杯，股份公司

解决方法

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