C语言深入讲解动态内存分配函数的使用

#include<stdlib.h>
#include<string.h>
#include<errno.h>
#include<stdio.h>
int main()
{
    int* p = (int*)malloc(10 * sizeof(int));
    if (p == NULL)
    {
        printf("%s\n", strerror(errno));
    }
    else
    {
        for (int i = 0; i < 10; ++i)
        {
            *(p + i) = i;
        }
        for (int i = 0; i < 10; ++i)
        {
            printf("%d ", *(p + i));
        }
    }
    free(p);
    p = NULL;
    /*
    1.断开指针与动态开辟的空间的联系，避免指针的危险操作
    2.防止对同一块动态空间内存空间的重复释放
    */
    return 0;
}

#include<stdio.h>
#include<stdlib.h>
int main()
{
    int* p = (int*)malloc(sizeof(int) * 10);
    if (p == NULL)
    {
        return 1;
    }
    for (int i = 0; i < 10; ++i)
    {
        *(p + i) = i;
    }
    for (int i = 0; i < 10; ++i)
    {
        printf("%d ", *(p++));//这里指针移动
    }
    free(p);//导致free释放的不是初始位置的指针，程序崩溃
    p = NULL;
    return 0;
}

#include <stdio.h>      /* printf, scanf, NULL */
#include <stdlib.h>     /* calloc, exit, free */
int main ()
{
  int i,n;
  int * pData;
  printf ("Amount of numbers to be entered: ");
  scanf ("%d",&i);
  pData = (int*) calloc (i,sizeof(int));
  if (pData==NULL) exit (1);
  for (n=0;n<i;n++)
  {
    printf ("Enter number #%d: ",n+1);
    scanf ("%d",&pData[n]);
  }
  printf ("You have entered: ");
  for (n=0;n<i;n++) printf ("%d ",pData[n]);
  free (pData);
  return 0;
}

#include <stdio.h>      /* printf, scanf, puts */
#include <stdlib.h>     /* realloc, free, exit, NULL */
int main ()
{
  int input,n;
  int count = 0;
  int* numbers = NULL;
  int* more_numbers = NULL;
  do {
     printf ("Enter an integer value (0 to end): ");
     scanf ("%d", &input);
     count++;
 
     more_numbers = (int*) realloc (numbers, count * sizeof(int));
 
     if (more_numbers!=NULL) {
       numbers=more_numbers;
       numbers[count-1]=input;
     }
     else {
       free (numbers);
       puts ("Error (re)allocating memory");
       exit (1);
     }
  } while (input!=0);
  printf ("Numbers entered: ");
  for (n=0;n<count;n++) printf ("%d ",numbers[n]);
  free (numbers);
  return 0;
}

#include<stdio.h>
#include<stdlib.h>
struct S
{
    int n;
    int arr[];
};
int main()
{
    struct S* ps = (struct S*)malloc(sizeof(struct S) + 5 * sizeof(int));
    //给arr分配内存20个字节的空间
    if (ps == NULL)
    {
        return 1;
    }
    //……………………操作
    free(ps);
    ps = NULL;
    return 0;
}