A typical memory leak problem in C language __c language

The specific questions are shown in the demo below:

#include <stdio.h>

void getheap (int *p)//p is a null address
{
	p = malloc (sizeof (int) *);//p points back to the space allocated in the heap The c3/>}//form parameter int *p in the stack space, the function is released after it is finished, and the space allocated by malloc is also lost, and no return of the argument


int main ()
{
	int *p = NULL;  NULL is (void *) 0
	printf ("p=%p\n", p);//p is a null address
	printf ("p=%p\n", &p);//&p is the address of P itself

	getheap (p //value passing, passing the null address to the formal parameter

	p[0] = ten;
	P[1] =;

	printf ("p[0]=%d,p[1]=%d\n", p[0],p[1]);
	
	Free (p);//p is not the first address of the space allocated in the heap, so free (p) also has a problem return

	0;
}

Run:

Reason:

Corrected as follows:

#include <stdio.h>


void getheap (int **p)/p is the address
{
	*p = malloc (sizeof (int) * 10) of S argument p; Assign the address of the space allocated in the heap to the argument p, that is, the argument p is the address of the allocated space in the heap after the end of the
}//function call, the value of the argument p is the first address of the allocated space in the heap,

int main ()
{
	int *p = NULL;

	Getheap (&P)//To pass the address of the pointer p itself to the formal parameter

       p[0] = ten;
	P[1] =;

	printf ("p[0]=%d,p[1]=%d\n", P[0], p[1]);

	Free (p); The value of the//p is the first address of the allocated space in the heap return

	0;
}

Running normally:

Because:

Where 0x100 is the address of P itself, the **p p in the formal parameter is 0x100,

*p=malloc (int) *10), assuming that the allocated space address is 0x123, the equivalent of the p=0x123 in the main function, that is, p points to the first address of the allocated space;

int *GETHEAP2 ()//correct: Returns the address of the heap of the application
{return
	malloc (MB);
}


Char *getstring ()//Error: Array is in the stack, after the function ends, the address disappears
{
	char array[10]= "Hello";
	return array;
}


Char getstring1 ()//correct: Returns the value, not the address, even if C is a variable in the stack, even if the address disappears
{
	char c= ' a ';
	return c;
}


const char *GETSTRING2 ()//correct: the constant is in the static area, the address always exists at the time the program is running
{
	return "hello";//the address of a constant can be returned as a return value of a function
} 


Char *getstring3 ()//correct:
{
	static char array[10]= "Hello";//return array in static area
	;
}


int main ()
{
	int *p=null;
	
	P=GETHEAP2 ()//correct
	
	char *s=getstring ()//Error
	
	char c=getstring1 ()//correct
	
	const char *s1=getstring2 ();// Correct
	
	const char *s2=getstring3 ();
	
	
	return 0;
}