C programs and differances between windows c compilers and gnu gcc

**Mikecore** · 10-02-2005

Hello I was doing a home work assignment for my C programming class and I came across a problem. The assignment is a simple program that demonstrates how to use the "continue" statement.

Code:

 

 
//      Fig. 4.12  fig04_12.c
//      Using the continue statement in a for statement

#include <stdio.h>

int main()

{

        int x;

        for ( x = 1; x <= 10; x++ ) {

                if ( x == 5 ) {

                         continue;

                }


                printf ( "%d ", x );

        }


        printf ( "\nUsed continue to skip printing the valve 5\n" );

        return 0;

}

I am coding on a linux laptop with gnu gcc 3.3.6, I found that when I compile it under gcc I get the wrong output, instead of skip printing the number 5 it prints it, and also never prints the last printf statement. When I compile it on a windozs box with Dev++ 4 from Bloodshed the same code runs with the correct output. Can anybody explain why this would be? I know they are two different compilers, but its a C statement shouldn't be the same for both.

**Hammer** · 10-02-2005

On the system that magically printed the 5, are you sure your source code is typed correctly?
The sample you've provided will give the following:

Code:

1 2 3 4 6 7 8 9 10
Used continue to skip printing the valve 5

**Mikecore** · 10-02-2005

I am positive I used the same code. for both compilers

this is the output I get under gcc

1
2
3
4
5
6
7
8
9
10
mike@laptop ~/code/C/chapter_4 $

**cwr** · 10-02-2005

I'm positive you didn't. In fact, why does your output above show a newline for each value, when your printf in the code has no \n?

Not only that, your output above has no "Used continue to skip printing the valve 5", but your code sample has code to print that.

Here's my output using gcc 3.3.3 (close enough):

Code:

$ gcc -v 2>&1 | tail -1
gcc version 3.3.3 (SuSE Linux)
$ cat > sample.c
//      Fig. 4.12  fig04_12.c
//      Using the continue statement in a for statement

#include <stdio.h>

int main()

{

        int x;

        for ( x = 1; x <= 10; x++ ) {

                if ( x == 5 ) {

                         continue;

                }


                printf ( "%d ", x );

        }


        printf ( "\nUsed continue to skip printing the valve 5\n" );

        return 0;

}
$ gcc -o sample sample.c -Wall
$ ./sample
1 2 3 4 6 7 8 9 10
Used continue to skip printing the valve 5
$

**quzah** · 10-02-2005

It is obviously not the same code, because you have no newlines in your for loop. It won't just randomly insert newlines for the hell of it.

Quzah.

**Mikecore** · 10-02-2005

Im sorry I don't know what I did I cut and pasted from your post and it worked fine
i must have gotten code mixed up im going back right now to ckeck it out

**Mikecore** · 10-02-2005

I just checked out my source files and I have a folder setup to hold all of my chapter_4
.c files. I have two file one called pg102.c and on called pg120.c the pg120.c was the code I
posted and every time i compiled it it did give me the wrong output. I checked my pg102.c
file and the output I was getting with all the /n is from the pg102.c program.

So it looks like for some reason it was running the pg102.c program instead of the pg120.c
program. I double and tripple checked it (to make sure I wasn't typing in ./pg102 instead of ./pg120) So i renamed the pg120.c file compiled it and it ran like it should.

cwr could you try this out on your system to verify im not a NUT !!.
you have the first code here is the second code.

Code:


//      Fig. 4.1: fig04_01.c
//      Counter-Controlled repetition

#include <stdio.h>

int main()

{

        int counter = 1;                     // declares variable "counter" as interger and sets it value to one

        while ( counter <= 10 ) {            // start of my while loop

                printf ( "%d\n", counter );
                ++counter;                   // pre-incrementing varivable "counter"
        }

        return 0;

}

just name them like i did. this one is pg102.c and the original is pg120.c and compile them in the same folder see if you get the same thing.

**Rashakil Fol** · 10-02-2005

The second piece of code would print out

Code:

After all, I don't see any continue statement.

**Mikecore** · 10-02-2005

Originally Posted by Rashakil Fol

The second piece of code would print out

Code:

After all, I don't see any continue statement.

I know what the output is going to be from the code I posted I wanted to know if he gets the same problem as I did. he is using a linux box like I am.

**cwr** · 10-02-2005

Yeah, I don't need to run it, the output is obvious, see Rashakil Fol's result.

**Mikecore** · 10-02-2005

I think your missing my point. why would it run the program ./pg102 when Im positive
I typed in ./pg120. it some how got the two programs mixed up.

**cwr** · 10-02-2005

Perhaps because you compiled it wrongly:

Code:

gcc -o pg120 pg102.c

Make sure you specified the correct output file as well as the correct source file.

I am certain the output is the same on my system, trust me. If you like I'll humour you and pretend to run it. Yep, the output is the same.

**Mikecore** · 10-02-2005

your right im a moron I must have done just what you said. Its late i must have screwed up
thanks for your time sorry I'm a nut job.

**cwr** · 10-02-2005

It's very, very rare to find a bug in gcc. And it's almost unheard of to find a bug where it won't compile really trivial programs like the one you gave above.

If a C program has no undefined, implementation defined, or unspecified behaviour, like the ones you posted above, the output will be the same on all platforms.

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C programs and differances between windows c compilers and gnu gcc

Ahhh

I think i figured out what was going on