C : printf function not printing when I input element of an array-CodePudding

I am trying to print an element of the cube_pattern string, but when I execute my code nothing is printed to the console and my code freezes for a few seconds:

#include <stdio.h>

#define SOLVED_CUBE "UUUUUUUUURRRRRRRRRFFFFFFFFFDDDDDDDDDLLLLLLLLLBBBBBBBBB"

char cube_pattern[54] = SOLVED_CUBE

void print_pattern() {
    printf("%s", cube_state[0]);
}

void main() {
    print_pattern();
}

I tried calling fflush(stdout) but it still doesn't work:

void print_pattern() {
    printf("%s", cube_state[0]);
    fflush(stdout);
}

CodePudding user response：

"UUUUUUUUURRRRRRRRRFFFFFFFFFDDDDDDDDDLLLLLLLLLBBBBBBBBB" contains 54 characters. Your char array only can store 54 characters. This does not leave space for a null terminator. Thus when you try to print using the %s specifier, you invoke undefined behavior. Maybe when it looks for the 55th character, it finds 0, but maybe not.

I don't see that using #define gains you anything. I would simply:

char cube_pattern[] = "UUUUUUUUURRRRRRRRRFFFFFFFFFDDDDDDDDDLLLLLLLLLBBBBBBBBB";

CodePudding user response：

Your code has multiple errors. First, you have multiple typos. For example, cube_state should be cube_pattern. Second, you are using the printf() formatter %s, but only passing it one character (cube_pattern[0]). Lastly, your array is only 54 bytes long, but your string needs 55 bytes (54 characters one NULL character).

This code works for me:

#include <stdio.h>

char cube_pattern[55] = "UUUUUUUUURRRRRRRRRFFFFFFFFFDDDDDDDDDLLLLLLLLLBBBBBBBBB";

void print_pattern() {
    printf("%s\n", cube_pattern);
}

int main() {
    print_pattern();
}

I have also changed printf("%s", cube_pattern); to printf("%s\n", cube_pattern);. Adding a new line will flush the buffer if your output is line-buffered, which is generally what you want. Alternatively, you could also use fflush(stdout).