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c - valgrind 地址在分配大小为 4 的块后为 0 字节

问题描述

我正在研究一个数学库。

create_vector创建一个维度为 n 的向量：(v1, v2, v3, ..., vn)

delete_vector释放内存。

struct Vector
{
    unsigned int dimension;
    double *components;
};
typedef struct Vector *vector_t;

vector_t create_vector(const unsigned int dimension)
{
    if(!dimension)
        return NULL;

    vector_t vector = (vector_t)malloc(sizeof(struct Vector));
    vector->dimension = dimension;
    vector->components = (double *)calloc(dimension, sizeof(double));

    return vector;
}

void delete_vector(vector_t *vector)
{
    if(*vector == NULL)
        return;

    free((*vector)->components);
    free(*vector);
    *vector = NULL;
}

主文件：

int main()
{
    vector_t vector1 = create_vector(3);
    delete_vector(&vector1);
}

在主文件中，我使用了这两个函数，但 valgrind 给了我这些警告。没有任何内存泄漏。我该如何解决？

==6906== Invalid write of size 4
==6906==    at 0x108800: create_vector (in /home/mrcoder/Scrivania/GitHub/libmath/test/testvector)
==6906==    by 0x10877E: main (in /home/mrcoder/Scrivania/GitHub/libmath/test/testvector)
==6906==  Address 0x4b3702c is 0 bytes after a block of size 4 alloc'd
==6906==    at 0x483021B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==6906==    by 0x1087DC: create_vector (in /home/mrcoder/Scrivania/GitHub/libmath/test/testvector)
==6906==    by 0x10877E: main (in /home/mrcoder/Scrivania/GitHub/libmath/test/testvector)
==6906==
==6906== Invalid read of size 4
==6906==    at 0x10882B: delete_vector (in /home/mrcoder/Scrivania/GitHub/libmath/test/testvector)
==6906==    by 0x108790: main (in /home/mrcoder/Scrivania/GitHub/libmath/test/testvector)
==6906==  Address 0x4b3702c is 0 bytes after a block of size 4 alloc'd
==6906==    at 0x483021B: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==6906==    by 0x1087DC: create_vector (in /home/mrcoder/Scrivania/GitHub/libmath/test/testvector)
==6906==    by 0x10877E: main (in /home/mrcoder/Scrivania/GitHub/libmath/test/testvector)
==6906==
==6906==
==6906== HEAP SUMMARY:
==6906==     in use at exit: 0 bytes in 0 blocks
==6906==   total heap usage: 2 allocs, 2 frees, 28 bytes allocated
==6906==
==6906== All heap blocks were freed -- no leaks are possible
==6906==
==6906== For counts of detected and suppressed errors, rerun with: -v
==6906== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

标签： cmemory-leaksmallocvalgrind

解决方案

你确定你不编译malloc(sizeof(vector_t));而不是 withmalloc(sizeof(struct Vector));吗？

大小为 4 的块分配表示您malloc只有 4 个字节是指针的大小如果您有 32b CPU，则结构的大小最小为 8 个字节

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