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C Assigning a pointer to a function

Why I can’t assign a point to a function. As you noticed in the following code. I cannot assign the pointer p1 by specifying the correct address after the function returns. But with the global * p pointer, I can store address information.

#include <stdio.h>
#include <stdlib.h>

int *p = NULL;
void test(int * pt1, int**pt2){
    p = (int*)malloc(sizeof(int));    
    pt1 = p;
    *pt2 = p;
    printf("p points to %p\n", p);
    printf("pt1 points to %p\n", pt1);
    printf("pt2 points to %p\n", *pt2);
}

int main(void) {
    int *p1 = NULL; 
    int *p2 = NULL;

    printf("p points to %p\n", p);
    printf("p1 points to %p\n", p1);
    printf("p2 points to %p\n", p2);

    test(p1, &p2);

    printf("p points to %p\n", p);
    printf("p1 points to %p\n", p1);
    printf("p2 points to %p\n", p2);

    return 0;
}

CONCLUSION:

p points to (nil)
p1 points to (nil)
p2 points to (nil)
p points to 0x8acb008
pt1 points to 0x8acb008
pt2 points to 0x8acb008
p points to 0x8acb008
p1 points to (nil)
p2 points to 0x8acb008
+5
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3 answers

Inside a testvariable pt1is a separate pointer. That is, it is not just an alias p1, but rather a copy that exists only for the call's lifetime.

, , , . test, pt1 .

, "" , pt2, "" :

#include <stdio.h>
#include <stdlib.h>

int *p = NULL;
int *test(int * pt1, int**pt2){
    p = (int*)malloc(sizeof(int));    
    pt1 = p;
    *pt2 = p;
    printf("p points to %p\n", p);
    printf("pt1 points to %p\n", pt1);
    printf("pt2 points to %p\n", *pt2);
    return pt1;
}

int main(void) {
    int *p1 = NULL; 
    int *p2 = NULL;

    printf("p points to %p\n", p);
    printf("p1 points to %p\n", p1);
    printf("p2 points to %p\n", p2);

    p1=test(p1, &p2);

    printf("p points to %p\n", p);
    printf("p1 points to %p\n", p1);
    printf("p2 points to %p\n", p2);

    return 0;
}
+4

arre p1 , . , p2, .

#include <stdio.h>
#include <stdlib.h>

int *p = NULL;
void test(int **pt1, int**pt2){
    p = (int*)malloc(sizeof(int));    
    *pt1 = p;
    *pt2 = p;
    printf("p points to %p\n", p);
    printf("pt1 points to %p\n", pt1);
    printf("pt2 points to %p\n", *pt2);
}

int main(void) {
    int *p1 = NULL; 
    int *p2 = NULL;

    printf("p points to %p\n", p);
    printf("p1 points to %p\n", p1);
    printf("p2 points to %p\n", p2);

    test(&p1, &p2);

    printf("p points to %p\n", p);
    printf("p1 points to %p\n", p1);
    printf("p2 points to %p\n", p2);

    return 0;
}
+1

p1 , main. p2 ( , &p2), .

+1

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