目前我正在学习类和构造函数。我修改了下面的代码。当我用valgrid运行代码时，它会给出存在内存问题的消息。我不知道这些是从哪来的。
#include <iostream>
class Container
{
...
public:
// constructors
Container() {
length = 0;
data = nullptr;
print("default constructor");}
Container(int len){
int lenght = len;
data = new double[lenght];
}
Container(std::initializer_list<double> il): Container(il.size())
{
std::copy(il.begin(), il.end(), data);
}
// destructor
// operators
void print(const std::string& info) const
{
// print the address of this instance, the attributes `length` and
// `data` and the `info` string
std::cout << " " << this << " " << length << " " << data << " "
<< info << std::endl;
}
private:
int length;
double* data;
};
int main()
{
Container x = {1,2,3,4};
std::cout << "x has address " << &x << std::endl;
return 0;
}
这是我从ValGrid得到的输出:
Valgrind detected memory issues:
==21== Memcheck, a memory error detector
==21== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==21== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==21== Command: ./temp_student_code
==21==
x has address 0x1fff000ca0
==21==
==21== HEAP SUMMARY:
==21== in use at exit: 74,035 bytes in 10 blocks
==21== total heap usage: 11 allocs, 1 frees, 74,091 bytes allocated
==21==
==21== 32 bytes in 1 blocks are definitely lost in loss record 1 of 6
==21== at 0x489F344: operator new[](unsigned long) (vg_replace_malloc.c:433)
==21== by 0x109379: Container::Container(int) (student_code.cpp:20)
==21== by 0x1093D8: Container::Container(std::initializer_list<double>) (student_code.cpp:23)
==21== by 0x109285: main (student_code.cpp:49)
==21==
==21== LEAK SUMMARY:
==21== definitely lost: 32 bytes in 1 blocks
==21== indirectly lost: 0 bytes in 0 blocks
==21== possibly lost: 0 bytes in 0 blocks
==21== still reachable: 74,003 bytes in 9 blocks
==21== suppressed: 0 bytes in 0 blocks
我自己也搞不清楚哪里出了问题。我可以得到一些关于如何解决内存问题的建议吗？
>
您缺少释放通过new手动分配的内存所需的析构函数。
您正在将长度保存在局部变量int lenght=len；中，您可能希望将其保存在类成员length中。
即。一个最小的例子是:
#include <iostream>
class Container
{
public:
// constructors
Container() = default() // no allocation!
Container(int len) : length(len) {
data = new double[len];
}
// destructor
~Container() {
if (data != nullptr) {
// need to release memory!
delete[] data;
}
// Other stuff ...
private:
int length = 0;
double* data = nullptr;
};
