Segmentation fault on strlen(char*) but char* IS terminated

Question

I've got a very very simple function which simply converts a char to a char* which represents the binary value of the char with 0's and 1's as chars.

char* stringToBin(char symbol) {
    int pos = 0;
    int value = (int) symbol;
    int rest;

    char* result = (char*) malloc(sizeof(char) * 9);

    while(value > 0) {
            if(value % 2 == 0) {
                    result[7-pos] = '0';
            }
            else {
                    result[7-pos] = '1';
            }
            pos++;
            value = value / 2;
    }

    while(pos < 8) {
            result[7-pos] = '0';
            pos++;
    }

    result[8] = '\0';

    puts(result);
    puts(strlen(result));

    return result;
}

My problem is I can't print the length of the char*. Printing the whole char* works perfect but not calculating the size. I alway get a segmentation fault. I think the problem is pretty simple but I did not get it right now. So please give me the missing hint ;)

Answer 1

The problem is not with the NUL-termination of your string, that's fine. Instead,

puts(strlen(result));

is wrong. puts() expects a C string, and you're giving it a size_t . Write instead:

printf("%zu\n", strlen(result));

(This assumes that the C99 format specifier %zu for size_t is available. If it isn't, then use:

printf("%u\n", (unsigned)strlen(result));

instead.)