Working on C

[wingnut2626]

Hey guys. Im working on learning C and I am having some trouble. I think whats going on is that the Book that I'm using to learn this is severly outdated. Basically I am trying to create a string, and print from the first place in the string on to the end (like reading a last name). Here is the code:


#include <stdio.h>


char name[20] = "Roy Hibbert";


int position= 0;


void main(){


while(name[position]!=' '){


position++;

}


printf(&name[position]);


}





and also there is a way to do it using pointers :


#include <stdio.h>


char name[20] = "Derrick Rose";


char *SurnameStart = name;


void main(){

while(*SurnameStart != ' '){

SurnameStart++;

}

SurnameStart++;

printf(SurnameStart);

}


Here is the warning that is generated when I attempt to compile either of these:

warning: format not a string literal and no format arguments [-Wformat-security]
printf(SurnameStart);

What am I doing wrong? And can someone explain to me the importance of pointers anyhow? Not even sure why these are necessary. Thanks in advance

[steeldriver]

Oops WRONG! see below...

[wingnut2626]

Thats crazy because this is how the book has it explicitly laid out....

[wingnut2626]

Is it possible that this is using a different version of C?

[steeldriver]

Oops sorry I misread your code

It compiles OK in gcc (even with -Wall -ansi -pedantic) even though 'SurnameStart' is not a string literal, I think ('name' is though)

How exactly are you trying to compile it?

[trent.josephsen]

Warnings are normal and expected; they don't necessarily mean you've done something wrong.

In this case the warning means that surnameStart can't be checked by the compiler, and if it contains any % specifiers, printf will try to use them (with possibly disastrous results). The defensive way to program this line is like this:

printf("%s", surnameStart);
(Also note that you should add "\n" to the end of the format string if you want to see the result.)

If you compile your code with -Wall -Wextra -std=c11 -pedantic, you'll also get an error saying that main() must return int. This is true in any standard version of C. If your book uses "void main()", do yourself a favor and get rid of it. (The book, I mean.)

Aside from that, your code has an awful lot of unnecessary blank lines, most of which I would remove. Readability counts.

[wingnut2626]

I just added a %s in there. Makes sense, that would be a formatted string. Wonder why the book has it like that? Maybe to make me start flying on my own?

[wingnut2626]

Yeah when I am finished, i take the blank lines out. They are in there so that i can print it out and write my own notes in there. For the future i will eliminate them before posting again. Thanks!