Question

当我运行以下代码时，我收到以下内存错误：

Filling an array at address 0x7ff0005c0 with 10 values
Done!
Filling an array at address 0x7ff0005bc with 1 values
Done!
Filling an array at address 0x7ff0005a0 with 4 values
Done!
Filling an array at address 0x4c30040 with 5 values
Done!
Filling an array at address 0x7ff000598 with 16 values
Done!
==30871== Invalid free() / delete / delete[] / realloc()
==30871==    at 0x4A07786: free (vg_replace_malloc.c:446)
==30871==    by 0x40081A: main (arrays.c:142)
==30871==  Address 0x500000002 is not stack'd, malloc'd or (recently) free'd
==30871== 
==30871== 
==30871== HEAP SUMMARY:
==30871==     in use at exit: 16 bytes in 1 blocks
==30871==   total heap usage: 2 allocs, 2 frees, 36 bytes allocated
==30871== 
==30871== LEAK SUMMARY:
==30871==    definitely lost: 16 bytes in 1 blocks
==30871==    indirectly lost: 0 bytes in 0 blocks
==30871==      possibly lost: 0 bytes in 0 blocks
==30871==    still reachable: 0 bytes in 0 blocks
==30871==         suppressed: 0 bytes in 0 blocks
==30871== Rerun with --leak-check=full to see details of leaked memory
==30871== 
==30871== For counts of detected and suppressed errors, rerun with: -v
==30871== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 2 from 2)

代码如下：

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

void fillArray(int* array, int len) {
  printf("Filling an array at address %p with %d "
         "values\n", array, len);
  for (int i = 0; i < len; ++i) {
    array[i] = i * 3 + 2;
    assert(array[i] == i * 3 + 2);
  }
  printf("Done!\n");
}


typedef struct {
  int a, b, c, d;
} FourInts;


int main(int argc, char* argv[]) {
  int array[10];

  fillArray(array, 10);

  int value;
  fillArray(&value, 1);
  assert(value == 2);

  FourInts four_ints;

  four_ints.a = 0;
  assert(four_ints.a == 0);

  fillArray((int*) &four_ints, 4);

  assert(four_ints.a == 2);
  assert(four_ints.b == 5);
  assert(four_ints.c == 8);
  assert(four_ints.d == 11);


  int* heap_array = (int*) malloc(sizeof(int) * 5);
  fillArray(heap_array, 5);

  free(heap_array);    
  FourInts* heapstruct=(FourInts*)malloc(sizeof(FourInts));
  fillArray((int*)&heapstruct,sizeof(FourInts));
  free(heapstruct);
  return 0;
}

我无法弄清楚内存泄漏是如何发生的。任何有关这方面的帮助将不胜感激！

Answer 1

heapstruct已经是一个指针，所以

fillArray((int*)&heapstruct,sizeof(FourInts));

获取指针的地址（产生指向指针的指针）。这会导致你忘记你不应该访问的记忆。

将其更改为

fillArray((int*)heapstruct,sizeof(FourInts));

Answer 2

除了@ Jefferey的答案之外，你还使用sizeof（FourInts）作为索引内部索引的上限，这会使你超出界限。正确（好吧，不太正确）是sizeof（FourInts）/ sizeof（int）。

调用函数时无效的free（）/ delete / delete [] / realloc（）错误

2 个答案: