Thread: How to fix Printing Errors

Hi,
Simply I'm tried to compile this code which is printing as what's shown in the printf .. I don't know it's displaying me on screen wrong results and don't know what's the logic Error in the code to fix it.

Code:

int main()
{
    char source[10], *des = strcpy(source, "012345678");
    printf("%d\n", sizeof(des));// didn't understand why it's giving me 8 instead of 9?! I'm having a pointer to string "012345678", pointer to string is also string!
    char *dest = (char *)malloc(strlen(source) + 1); // +1 for nill value, right?! I reckon on that.
    for (int i = 1; i <= strlen(source);i++)
        dest[i] = source[i];
    dest[strlen(source) + 1] = '\0';
    printf("dest = %s", dest); // I dont know what's the wrong here its printing me "12345678" and "not 012345678" !!!
}

thanks for your help!

Originally Posted by laserlight

You don't need strcpy for this. Use initialisation:

Code:

char source[10] = "012345678", *des = source;

As for your confusion: you invoked sizeof on the pointer named des, so of course you got the result of the number of bytes in a pointer. I don't know why you expect to get 9 rather than 10 though: the underlying array source has 10 chars, so sizeof(source) will result in 10, not 9.
source is null terminated, so the typical approach for copying into your new dynamic array is just to copy from the char at index 0 (not 1, which is why you noticed '0' missing) until you reach the null character, and just copy that too and end. If you really want to call strlen, call it once and save the result to reuse.

I didn't understand what you said on "the number of bytes in a pointer", in other words, aren't the byte of pointer is the same byte of the value that's the pointer pointing at?! and is the bytes's size of a pointer regardless to its type constant?!
and for reaching the null character, is there more sympathetic way than source[i] != '\0'?! thanks !!

In addition, what I understand from you that the "pointer" is a variable and once I sizeof that pointer, we are getting the bytes that's the pointer itself holding "regardless to what's he pointing at!" .

Originally Posted by laserlight

Think about sizeof(int). The result of that is going to be the same whether the int has a value of 10 or 10000. Likewise, the result of sizeof(char*) is going to be the same whether the char* points to the first character of a 10 char string or the first character of a 10000 char string.

What do you mean by "sympathetic" regarding code?

meaning like source !=NULL

Originally Posted by laserlight

Think about sizeof(int). The result of that is going to be the same whether the int has a value of 10 or 10000. Likewise, the result of sizeof(char*) is going to be the same whether the char* points to the first character of a 10 char string or the first character of a 10000 char string.

What do you mean by "sympathetic" regarding code?

and is the byte of pointer constant regardless to what's pointing on? meaning sizeof(char*) is the same sizeof(int*) and the same as sizeof(float*) ... etc ...?

Originally Posted by laserlight

That doesn't make sense to me: what's wrong with source[i] != '\0'?

Nothing wrong but they just said here over our forum there's a way to write something more sympathetic to code by using *source != NULL or something like that .. just forget

Originally Posted by laserlight

Probably, but that's not guaranteed.

Alright, thanks !
Moreover, the size of (STRUCT) is depending on what we are declaring inside it, right? meaning if I build a struct like that

Code:

struct DENT
{
   int a;
}

;
so the sizeof(DENT) will be sizeof (int) only, right?!

Originally Posted by laserlight

There's no reason for it not to be, but in other cases you may find padding complicates the calculation.

THANKS!
Another lily question!
I have seen over here in the forum that we always want to keep the '\0' in ARRAY[strlen(<string>)-1], why specifically -1? we can keep it ARRAY[strlen(<string>)] and its allowed not going to overlapping or something !