Strange behavior of simple For loop in C language

Asked Aug 30 '13 at 13:12

Active Aug 30 '13 at 13:21

Viewed 63 times

I was just curious to do it and find the result, but I got really shocked...

Actually,

when we do this:

for(i=0; 0; i++)
 printf("hello");

it prints hello... which it should not.

and if do like this:

int a=0;
for(i=0;a;i++)
 printf("hello");

it doesn't print hello...

although the expected behavior is shown in if-else or while loop.. Can anyone explain?

edited Aug 30 '13 at 13:21

alk

69,737
10
105
255

asked Aug 30 '13 at 13:12

nsthethunderbolt

2,059
1
17
24

2

What compiler are you using and what system are you on? I can not reproduce the first one. – Shafik Yaghmour Aug 30 '13 at 13:14
windows 7, turbo-c using dos-box – nsthethunderbolt Aug 30 '13 at 13:14
8

Are you sure you didn't type `for(i=0; 0; i++);` by mistake? – unwind Aug 30 '13 at 13:17
Maybe some issues outside the shown code? In C, it's possible to modify things on the stack unintentionally, for example. – Andrey Moiseev Aug 30 '13 at 13:18
2

Did you copy-paste the example, or did you retype it from memory? I suspect you had an extra `;` at the end of the first line of your first snippet. – user4815162342 Aug 30 '13 at 13:18
1

Try to copy-paste your code to https://ideone.com and see if it reproduces there, if so, give us the link (putting your complete source (copy-pasted, not rewritten) as is in the question is always a good idea; if it's too long, you should construct an [SSCCE](http://sscce.org/)). – Bernhard Barker Aug 30 '13 at 13:18
1

@unwind No i didn't.. i am sure.. although it gives me a warning that the code is unreachable.. then also it prints hello – nsthethunderbolt Aug 30 '13 at 13:19
@Dukeling I would not have even thought to look but you actually found a dup that looks like it explains this! – Shafik Yaghmour Aug 30 '13 at 13:24
@ShafikYaghmour but i didn't get how that is relevant or explaining my question.. – nsthethunderbolt Aug 30 '13 at 13:27
@nsthethunderbolt The compiler is buggy, that's it. – Andrey Moiseev Aug 30 '13 at 13:29
@nsthethunderbolt if you read all the answers and comments the consensus is that it is a bug and I would agree. – Shafik Yaghmour Aug 30 '13 at 13:29
@ShafikYaghmour ok thanks a lot... i thought it's some kind of a deep concept...:) – nsthethunderbolt Aug 30 '13 at 13:30

Strange behavior of simple For loop in C language

0 Answers0