如何解决C ++指针和堆释放
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
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