CODEWITHSUNDEEP
cnullputs
Destructor
Destructor

Reputation: 14438

what happens if puts() function doesn't encounter null character?

Consider following program.

#include <stdio.h>
int main(void)
{
    char side_a[] = "Side A";
    char dont[] = {'W', 'O', 'W', '!' }; 
    char side_b[] = "Side B";
    puts(dont); /* dont is not a string */
    return 0;
}

I know that puts() function stops when it encounters the null character. But in above program I haven't specified null character. So when it stops printing? Is this program invokes undefined behavior? Is it guaranteed to get same output for this program on various C compilers? What the C standard says about this?

Upvotes: 1

Views: 869

Answers (3)

Amol Saindane
Amol Saindane

Reputation: 1598

Yeah it will be Undefined Behaviour, so output won't be same all the time. If you want to print in such case, I would suggest as below to have uniform output:

printf("%.*s", 4, dont);

Upvotes: 2

Jens Gustedt
Jens Gustedt

Reputation: 78923

Yes, this error results in your program having no defined behavior. As the term indicates, you can't expect anything reasonable to come out of the execution of such a program.

Upvotes: 3

Mat
Mat

Reputation: 206699

puts will end up reading past the last element of dont, which is undefined behavior.

So no, you are not guaranteed the same output every time. You're not guaranteed any output at all for that matter - you're not guaranteed anything since this is undefined behavior.

Upvotes: 4

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