Question

以下是代码的简化版本，我删除了与问题无关的所有内容。

#include <iostream>
#define N 3

int main() {

    int *input;
    int **cl;

    input = new int[N];
    cl = new int*[N];
    for(int i = 0; i < N; i++) {
        cl[i] = new int[N];
    }


    for(int i = 0; i < N; i++) {
        delete[] cl[i];
    }
    delete[] cl;
    delete[] input;

    return 0;
}

valgrind输出：

==5782== HEAP SUMMARY:
==5782==     in use at exit: 72,704 bytes in 1 blocks
==5782==   total heap usage: 6 allocs, 5 frees, 72,776 bytes allocated
==5782== 
==5782== 72,704 bytes in 1 blocks are still reachable in loss record 1 of 1
==5782==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==5782==    by 0x4EC3EFF: ??? (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21)
==5782==    by 0x40104E9: call_init.part.0 (dl-init.c:72)
==5782==    by 0x40105FA: call_init (dl-init.c:30)
==5782==    by 0x40105FA: _dl_init (dl-init.c:120)
==5782==    by 0x4000CF9: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)
==5782== 
==5782== LEAK SUMMARY:
==5782==    definitely lost: 0 bytes in 0 blocks
==5782==    indirectly lost: 0 bytes in 0 blocks
==5782==      possibly lost: 0 bytes in 0 blocks
==5782==    still reachable: 72,704 bytes in 1 blocks
==5782==         suppressed: 0 bytes in 0 blocks
==5782== 
==5782== For counts of detected and suppressed errors, rerun with: -v
==5782== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

我刚开始学习C ++，也许有一些我看不到的愚蠢错误。

我知道我还应该检查一下分配时是否没有“内存不足”错误，但我忽略它以便代码更清晰。我也知道我可以使用例如向量并不关心分配，但我仍然担心我做错了什么。

Answer 1

C ++为您提供了为您封装内存管理的工具。

#include <iostream>
#include <vector>

int main() {
    // read the size for the vectors
    int n;
    std::cin >> n >> '\n';

    // allocate vector with n elements
    auto input = std::vector<int>{n};

    // read the elements
    for(int i = 0; i < n; i++) {
        std::cin >> std::setw(1) >> input[i];
    }
    // print them
    for(const auto& d : input) {
        std::cout << d << std::endl;
    }

    // allocate the vectors and store 1 in each field.
    auto Cl = std::vector<std::vector<int>>{n, std::vector<int>{n, 1}};
    auto Cr = std::vector<std::vector<int>>{n, std::vector<int>{n, 1}};

    return 0;

    // will safely release all the memory here.
}

这看起来更像C ++，而不像C语言。向量将自动为您处理所有内存管理。

注意：我没有测试过这段代码，所以它可能包含一些错误。我假设C ++ 11语法，但是也应该很容易将代码更改为旧的C ++语法。

Answer 2

现在您已经添加了valgrind输出，它显然与在此处有答案的问题相同：Valgrind: Memory still reachable with trivial program using <iostream>

简短的故事是，导致该报告的不是您的代码。你可以删除main()中的所有内容，然后返回，valgrind仍然会泄漏。

阅读该问题的已接受答案以获得解释。

valgrind检测到内存泄漏，但找不到我忘记释放的行

2 个答案: