C: 重新分配内存 valgrind 时出错

你好！编写了一个从二维数组中删除字符串的程序。一切似乎都正常工作，但 valgrind 显示内存丢失和错误。请告诉我我做错了什么。

#include "cdio.h"
#include "func.h"

int del(long int **matrix, size_t *n, int pos)
{
    free(matrix[pos]);

    for (size_t i = pos; i < *n-1; i++)
        matrix[i] = matrix[i+1];
    *n -= 1;

    long int **temp = realloc(matrix, *n * sizeof(long int *));

    if (temp)
    {
        matrix = temp;
        temp = NULL;
    }

    return SUCCESS;
}

int main()
{
    long int **matrix = NULL;
    size_t n = 5;
    size_t m = 4;

    matrix = matrix_allocate(n, m);

    for (size_t i = 0; i < n; i++)
        for (size_t j = 0; j < m; j++)
            matrix[i][j] = rand() % 100;

    puts("OLD MATRIX:");
    print_matrix(matrix, n, m);

    int pos = 0;

    puts("enter position:");
    scanf("%d", &pos);

    del(matrix, &n, pos);


    puts("NEW MATRIX:");
    print_matrix(matrix, n, m);

    for (int i = 0; i < n; i++)
        free(matrix[i]);

    free(matrix);

    return 0;
}

OLD MATRIX:
83 86 77 15 
93 35 86 92 
49 21 62 27 
90 59 63 26 
40 26 72 36 
enter position:
1

NEW MATRIX:
==3691== Invalid read of size 8
==3691==    at 0x108E30: print_matrix (cdio.c:60)
==3691==    by 0x108B86: main (del.c:47)
==3691==  Address 0x522d040 is 0 bytes inside a block of size 40 free'd
==3691==    at 0x4C31D2F: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3691==    by 0x108A1C: del (del.c:12)
==3691==    by 0x108B63: main (del.c:43)
==3691==  Block was alloc'd at
==3691==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3691==    by 0x108C11: matrix_allocate (cdio.c:8)
==3691==    by 0x108A80: main (del.c:29)
==3691== 
83 86 77 15 
49 21 62 27 
90 59 63 26 
40 26 72 36 
==3741== Invalid read of size 8
==3741==    at 0x108BA4: main (del.c:50)
==3741==  Address 0x522d040 is 0 bytes inside a block of size 40 free'd
==3741==    at 0x4C31D2F: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3741==    by 0x108A1C: del (del.c:12)
==3741==    by 0x108B63: main (del.c:43)
==3741==  Block was alloc'd at
==3741==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3741==    by 0x108C11: matrix_allocate (cdio.c:8)
==3741==    by 0x108A80: main (del.c:29)
==3741== 
==3741== Invalid free() / delete / delete[] / realloc()
==3741==    at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3741==    by 0x108BCD: main (del.c:52)
==3741==  Address 0x522d040 is 0 bytes inside a block of size 40 free'd
==3741==    at 0x4C31D2F: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3741==    by 0x108A1C: del (del.c:12)
==3741==    by 0x108B63: main (del.c:43)
==3741==  Block was alloc'd at
==3741==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==3741==    by 0x108C11: matrix_allocate (cdio.c:8)
==3741==    by 0x108A80: main (del.c:29)