Common errors in C++ dynamic memory allocation

1. The requested memory is released multiple times

int main(void){
    
    
	int *p = new int[10];

	p[0] = 100;
	printf("p[0]'s value: %d\n",*p);

	delete[] p;	//释放内存
	
	delete[] p;

	return 0;
}

2. Memory leak-memory has not been released after application

int main(void){
    
    
	int *p = new int[1024];

	p[0] = 100;
	printf("p[0]'s value: %d\n",*p);

	while(1){
    
    
		*p++;
	}

	system("pause");
	return 0;
}

3. The released memory is not the address at the time of application

int main(void){
    
    
	int *p = new int[1024];

	p[0] = 100;
	printf("p[0]'s value: %d\n",*p);

	for(int i=0; i<10; i++){
    
    
		*p++;
	}

	delete[] p;	//释放内存

	return 0;
}

4. Release the null pointer.
There may be an error, but you can’t write like this if you don’t report an error.

int main(void){
    
    
	int *p = NULL;

	if(1==0){
    
    
		p = new int;
	}
		
	delete p;	//释放内存
	
	return 0;
}

5. Release a memory block, but continue to reference its contents

int main(void){
    
    
	int *p = new int[10];
	delete p;	//释放内存
	
	p[0] = 100;
	printf("p[0]'s value: %d\n",*p);

	return 0;
}

6. Cross-border access

int main(void){
    
    

// 越界访问 
	int *p = new int[10];
	memset(p,0,18*sizeof(int));

	for(int i=0; i<10; i++){
    
    
		printf("*p's value: %d\n",*p++);
	}

	for(int i=0; i<10; i++){
    
    
		printf("*p's value: %d\n",*p++);
	}

	return 0;
}