Question

我正在运行ASAN，目的是在一个非常大的项目中查找内存泄漏。我已找到原因，但不知道如何解决。我制作了一个示例程序来使问题易于理解。在下面的程序中，我只能解决指定的代码。对于其余的代码，无法解决。因此，请提出以下可能需要解决的解决方案：ASAN错误。（如何使用t1将指针二设为NULL？）

#include<stdio.h>
#include<stdlib.h>

typedef struct l
{
    int a, b;
}pack;

void delete_me(pack *ap)
{
    free(ap);
}

int main(void)
{
    pack **d_ptr = (pack **)malloc(3 * sizeof(pack *));
    pack *one, *two, *three;
    one = (pack *)malloc(sizeof(pack));
    one->a = 1, one->b = 2;
    two = (pack *)malloc(sizeof(pack));
    two->a = 3, two->b = 4;
    three = (pack *)malloc(sizeof(pack));
    three->a = 5, three->b = 6;
    d_ptr[0] = one;
    d_ptr[1] = two;
    d_ptr[2] = three;

    // I can Only work-around below code (4 lines)
    pack *t1 = d_ptr[1]; // For which index t1 would be assigned, is not known before hand
    t1->a = 1; t1->b = 2;
    printf("a: %d, b: %d\n", two->a, two->b);
    delete_me(t1); // How to delete t1 so that corresponding pointer also becomes NULL?
    // Work around only till here was possible.

    // Below this, No workaround possible.
    if (two && (two->a == one->a)) // ASAN ERROR
            printf("ERROR\n");
    else
            printf("It works!\n");
    return 0;
}

ASAN错误：错误：AddressSanitizer：释放后使用堆

Answer 1

不幸的是，您的问题并不能真正解决。

例如，同一指针有多个副本时，

int *p1 = malloc(sizeof (int));
int *p2 = p1;
int *p3 = p2;

然后释放它们中的任何一个会使它们全部失效：

free(p2);
// Now p1, p2, p3 have invalid values.
// The C standard calls these "indeterminate values"; accessing them has undefined behavior

释放后，您可以手动将p2设置为NULL，但这仍然使p1和p3悬空。您无法自动找到程序内存中任何地方可能存在的指针值的所有副本。

您需要重组程序的逻辑。没有快速简便的修复方法。

释放后使用ASAN堆

1 个答案: