C语言 超详细梳理总结动态内存管理

int a = 10；//在栈空间开辟4个字节的连续空间
int b[20] = { 0 };//在栈空间开辟20个字节的连续空间

int N;
scanf("%d",&N);
int a[N]={ 0 };

#include<stdio.h>
#include<stdlib.h>
 
int main()
{
	int* p = (int*)malloc(40);//开辟40个字节的栈空间
	if (p == NULL)            //检查是否为空指针
	{
		perror("malloc");
		return 1;
	}
	for (int i = 0; i < 10; i++)
	{
		*(p + i)=i;
	}
	free(p);                 //用完后释放空间，注意参数为首地址
	p = NULL;                //置为空指针
}    

#include<stdio.h>
#include<stdlib.h>
 
int main()
{
	int* p = (int*)calloc(10, sizeof(int));
	if (p == NULL)
	{
		perror("calloc");
		return 1;
	}
	for (int i = 0; i < 10; i++)
	{
		printf("%d  ", *(p + i)); //输出为 10个0
	}
	free(p);
	p = NULL;
}

void test()
{
    int *p = (int*)malloc(INT_MAX/4);
    *p = 20;
    free(p);
}

int main()
{
	int* p = (int*)calloc(10, sizeof(int));
	if (p == NULL)
	{
		perror("calloc");
		return 1;
	}
	for (int i = 0; i <= 10; i++)  //当i为10时，形成越界访问，程序出错
	{
		printf("%d  ", *(p + i));
	}
	free(p);
	p = NULL;
}

    int a = 10;
	int* p = &a;
	free(p);

void test()
{
	int* p = (int*)malloc(100);
	p++;
	free(p);
}

void test()
{
	int* p = (int*)malloc(100);
	free(p);
	free(p);
}

void GetMemory(char* p)            //对空指针解引用
{
	p = (char*)malloc(100);        //内存泄露
}
void test()
{
	char* str = NULL;
	GetMemory(str);
	strcpy(str, "hello world");    
	printf(str);
}
 
int main()
{
	test();
 
}

char *GetMemory(void)
{
	char p[] = "hello world";
	return p;
}
void test()
{
	char* str = NULL;
	str=GetMemory();        //野指针str
	printf(str);
}
 
int main()
{
	test();
 
}

void GetMemory(char** p,int num)            //传址调用
{
	*p = (char*)malloc(num);        
}
void test()
{
	char* str = NULL;
	GetMemory(&str,100);
	strcpy(str, "hello world");
	printf(str);                                
                                            //没有free
}
 
int main()
{
	test();
 
}

void GetMemory(char** p,int num)
{
	*p = (char*)malloc(num);
}
void test()
{
	char* str = (char*)malloc(100);
	strcpy(str, "hello world");
	free(str);                            //还给你，我还要用,哼~
	if (str != NULL)
	{
		strcpy(str, "!!!");
		printf(str);
	}
}
 
int main()
{
	test();
 
}