warning: assignment makes integer from pointer without a cast

Question

#include <stdio.h>
#include <string.h>
#include <math.h>
#define NUM 8

int main() {
    int i, len, sum, offset, remain;
    char bin[32];
    char hexlist[6][1] = {"A", "B", "C", "D", "E", "F"};
    char hex[NUM] = "00000000";
    int hexlen = NUM;
    while (1) {
        scanf("%s", bin);
        if (strcmp(bin, "0") == 0) {
            break;
        }
        len = strlen(bin);
        offset = 0;
        while (offset < len) {
            sum = 0;

            if (len - offset >= 4) {
                for (i = 0; i < 4; i++) {
                    sum += (bin[len-1-i-offset] - '0') * pow(2, i);
                }
            }
            else {
                remain = len - offset;
                for (i = 0; i < remain; i++) {
                    sum += (bin[len-1-i-offset] - '0') * pow(2, i);
                }
            }

            if (sum > 10)
                // I got "warning: assignment makes integer from pointer without a cast"
                hex[--hexlen] = hexlist[sum%10];
            else
                hex[--hexlen] = (char)(((int)'0')+sum);

            offset += 4;
        }
        printf("%s\n", hex);
    }
    return 0;
}

I tried hex[--hexlen] = (char)hexlist[sum%10];, but I got "warning: cast from pointer to integer of different size"

orlp · Accepted Answer · 2011-05-05 22:00:47Z

4

What you want is this:

char hexlist[] = {'A', 'B', 'C', 'D', 'E', 'F'};

In C a character constant between double quotes indicates a string of characters, and is ended with a null character \0. A character constant between single quotes indicates a single character.

edited May 5, 2011 at 22:00

answered May 5, 2011 at 21:53

orlp

119k39 gold badges226 silver badges324 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Fred Larson Over a year ago

Yeah, or char hexlist[] = "ABCDEF";.

orlp Over a year ago

Fred Larson: You are right, and normally I would agree, but in this case an array of character constants seems more appropriate then a string.

Fred Larson Over a year ago

@nightcracker, @pmg: I know. But for brevity's sake, I'd be inclined to waste the byte. Doesn't make much difference to me.

Vayn Over a year ago

Thank you all so much. I've just learned C a week ago, I don't understand pointer clearly. Now my code works well (after I corrected the other errors). I don't know is it appropriate, but I want to know how I add every char to an array dynamically? Not just a predefined char array char hex[NUM] = "00000000".

pmg Over a year ago

@Vayn: it's better to post a new question rather than ask one in a comment.

|

pmg · Accepted Answer · 2011-05-05 21:55:34Z

1

hexlist is an array of arrays

char hexlist[6][1];

each element of hexlist is an array ... and usually references to such arrays decay to pointers. That's what is hapenning in your code: hexlist[sum % 10] is an object of type char[1] and decays to a pointer.

You then try to assign that pointer to an element of hex, of type char. The types are incompatible and after the default promotions, the compiler complains.

answered May 5, 2011 at 21:55

pmg

109k14 gold badges132 silver badges203 bronze badges

2 Comments

pmg Over a year ago

No. In many uses, arrays decay to a pointer to their first element. Read section 6 of the comp.lang.c FAQ ... and, once you're there, all the other sections too :)

Vayn Over a year ago

The FAQ is nice! Thank you :D

Collectives™ on Stack Overflow

warning: assignment makes integer from pointer without a cast

2 Answers 2

6 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related