warning: assignment from incompatible pointer type [enabled by default] and cast to pointer from integer of different size [-Wint-to-pointer-cast]

Question

when i try to run my code, there got warning and i don't know why....Please help me, this is my code:

#include<stdio.h>
#include<stdlib.h>
#include<sys/time.h>

#define TESTTIMES 2000


void test1()
{
    // printf("--------TEST1----------\n");
    int i = 0;
    for (i = 0; i < 150; i++) {
        char *p = (char*)MyMalloc(1);
        MyFree(p);
    }
}


void test2()
{
    // printf("--------TEST2----------\n");
    int *a[150], i;
    for (i = 0; i < 150; i++) {
        char *p = (char*)MyMalloc(1);
        a[i] = p;
        if ((i + 1) % 50 == 0) {
            int j = i + 1  - 50;
            while (j <= i) {
                MyFree(a[j]);
                j += 1;
            }
        }
    }
}

void test3()
{
    // printf("--------TEST3----------\n");
    int flag, cnt = 0, top = 0;
    char *b[50];

    srand(time(NULL));
    while(cnt < 50) {
        flag = rand() % 2;
        if (flag) {
            char *p = (char*)MyMalloc(1);
            b[top] = p;
            top++;
            cnt += 1;
        } else {
            if (top > 0) {
                top -= 1;
                MyFree(b[top]);
            }
        }
    }
    while (top > 0) {
        top--;
        MyFree(b[top]);
    }
}

void test4() 
{
    // printf("--------TEST4----------\n");
    int flag, size, cnt = 0, top = 0;
    char *b[50];

    srand(time(NULL));
    while(cnt < 50) {
        flag = rand() % 2;
        size = rand() % 64 + 1;
        if (flag) {
            char *p = (char*)MyMalloc(size);
            b[top] = p;
            top++;
            cnt += 1;
        } else {
            if (top > 0) {
                top -= 1;
                MyFree(b[top]);
            }
        }
    }
    while (top > 0) {
        top--;
        MyFree(b[top]);
    }
}

void test5()
{
    // printf("--------TEST5----------\n");
    int i = 0;
    while (i < TESTTIMES) {
        char *p = MyMalloc(4096);
        MyFree(p);
        i++;
    }
}

void test6()
{
    // printf("--------TEST6----------\n");

    int top = 0, i = 0;
    char *b[100];

    while(1) {
        char *p = (char*)MyMalloc(100); 
        if (p) {
            b[top] = p;
            top++;
        } else {
            break;
        }
    }

    while(i < top){
        MyFree(b[i]);
        i++;
    }
}

and I got warning on these lines:

ind.c: In function \u2018test1\u2019:
ind.c:79:19: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
         char *p = (char*)MyMalloc(1);
                   ^
ind.c: In function \u2018test2\u2019:
ind.c:90:19: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
         char *p = (char*)MyMalloc(1);
                   ^
ind.c:91:14: warning: assignment from incompatible pointer type [enabled by default]
         a[i] = p;
              ^
ind.c: In function \u2018test3\u2019:
ind.c:112:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
             char *p = (char*)MyMalloc(1);
                       ^
ind.c: In function \u2018test4\u2019:
ind.c:140:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
             char *p = (char*)MyMalloc(size);
                       ^
ind.c: In function \u2018test5\u2019:
ind.c:162:19: warning: initialization makes pointer from integer without a cast [enabled by default]
         char *p = MyMalloc(4096);
                   ^
ind.c: In function \u2018test6\u2019:
ind.c:176:19: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
         char *p = (char*)MyMalloc(100); 
                   ^

is it because of different GCC version? How can I fix it? It is C programming, I got two warnings such as warning: assignment from incompatible pointer type [enabled by default] and cast to pointer from integer of different size [-Wint-to-pointer-cast].

Answer 1

The reason you're getting these errors:

warning: cast to pointer from integer of different size

Is because your main file doesn't know how MyMalloc is defined, so it defaults to a function returning an int. You can fix this by putting #include "mymalloc.h" at the top of your main file.

If you do this, you'll see another error, specifically that buffer and memory are defined twice. This is because you're defining these two variables in your header file. It is for this reason that variables shouldn't be defined in a header file.

Since you only use buffer and memory in mymalloc.c, you should move them into that file. That way you avoid the multiple definition error. You should also move struct node for the same reason.