Why does the answer is 0?

[±èµ¿±Õ]

#include"stdio.h"

main()
{
int a = 128 * 128 * 128 * 128 * 128 * 128 * 128 * 128 ;
int a1 = 256 * 256 * 256 * 256;
char b = 256 * 256 * 256 * 256;
long c = 256 * 256 * 256 * 256;
float d = 512 * 512;
double e = 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 *
64 * 64 * 64;
double e1 = 256 * 256 * 256 * 256;
printf("a= %d \nb= %d \nc= %d \nd= %d \nd= %f \ne=%lf \n", a,b,c,d,d,e);
printf("a1= %d \ne1=%lf\n",a1,e1);
}

//anyway, all the same , 0 !!!

[Barry Schwarz]

On Mon, 28 Mar 2005 14:17:49 +0900, "±èµ¿±Õ"
<na*******@game.hs.kr.NOSPAMOK> wrote:

#include"stdio.h"

main()
{
int a = 128 * 128 * 128 * 128 * 128 * 128 * 128 * 128 ;
int a1 = 256 * 256 * 256 * 256;
char b = 256 * 256 * 256 * 256;
long c = 256 * 256 * 256 * 256;
float d = 512 * 512;
double e = 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 *
64 * 64 * 64;
double e1 = 256 * 256 * 256 * 256;
printf("a= %d \nb= %d \nc= %d \nd= %d \nd= %f \ne=%lf \n", a,b,c,d,d,e);
printf("a1= %d \ne1=%lf\n",a1,e1);
}

//anyway, all the same , 0 !!!

Unless sizeof(int) is greater than four on your system, most of your
code invokes undefined behavior. If sizeof(int) is two, then d also
invokes undefined behavior. The first printf also.

Even if your compiler generates the "expected" code and merely
truncates the values, the lower order portion of each result is always
zero.

Pick an easy one, like d, and work it out in hex.


<<Remove the del for email>>

[Keith Thompson]

do*@dot.dot writes:

On Mon, 28 Mar 2005 14:17:49 +0900, "±èµ¿±Õ" <na*******@game.hs.kr.NOSPAMOK>
wrote:

[...]

char b = 256 * 256 * 256 * 256;

An obvious overflow ... char = -128 to + 127

Or 0 to 255 (if plain char is unsigned), or -127 to +127 (if plain
char is signed but not two's-complement), or other ranges if
CHAR_BIT > 8.

--
Keith Thompson (The_Other_Keith) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[manoj1978]

±èµ¿±Õ wrote:

#include"stdio.h"

main()
{
int a = 128 * 128 * 128 * 128 * 128 * 128 * 128 * 128 ;
int a1 = 256 * 256 * 256 * 256;
char b = 256 * 256 * 256 * 256;
long c = 256 * 256 * 256 * 256;
float d = 512 * 512;
double e = 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64;
double e1 = 256 * 256 * 256 * 256; put a cast on right side for double,otherwise expression will be an
int and will overflow and it will be undefined behaviour.
in all other cases right hand side expression will over flow 4 byte
int. printf("a= %d \nb= %d \nc= %d \nd= %d \nd= %f \ne=%lf \n", a,b,c,d,d,e); printf("a1= %d \ne1=%lf\n",a1,e1);
}

//anyway, all the same , 0 !!!

[CBFalconer]

"±èµ¿±Õ" wrote:

#include"stdio.h"

main()
{
int a = 128 * 128 * 128 * 128 * 128 * 128 * 128 * 128 ;
int a1 = 256 * 256 * 256 * 256;
char b = 256 * 256 * 256 * 256;
long c = 256 * 256 * 256 * 256;
float d = 512 * 512;
double e = 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 * 64 *
64 * 64 * 64 * 64 * 64 * 64;
double e1 = 256 * 256 * 256 * 256;
printf("a= %d \nb= %d \nc= %d \nd= %d \nd= %f \ne=%lf \n", a,b,c,d,d,e); printf("a1= %d \ne1=%lf\n",a1,e1);
}

//anyway, all the same , 0 !!!

Absolutely correct. 0 is a suitable value of undefined behaviour.

--
"If you want to post a followup via groups.google.com, don't use
the broken "Reply" link at the bottom of the article. Click on
"show options" at the top of the article, then click on the
"Reply" at the bottom of the article headers." - Keith Thompson

[Mark McIntyre]

On Mon, 28 Mar 2005 14:17:49 +0900, in comp.lang.c , "±èµ¿±Õ"
<na*******@game.hs.kr.NOSPAMOK> wrote:

int a = 128 * 128 * 128 * 128 * 128 * 128 * 128 * 128 ;
Compiling...
clc_test.c
g:\users\mark\c\clc_tests\clc_test.c(5) : warning C4307: '*' :
integral constant overflow
g:\users\mark\c\clc_tests\clc_test.c(6) : warning C4307: '*' :
integral constant overflow
g:\users\mark\c\clc_tests\clc_test.c(7) : warning C4307: '*' :
integral constant overflow
g:\users\mark\c\clc_tests\clc_test.c(8) : warning C4307: '*' :
integral constant overflow
g:\users\mark\c\clc_tests\clc_test.c(10) : warning C4307: '*' :
integral constant overflow
g:\users\mark\c\clc_tests\clc_test.c(12) : warning C4307: '*' :
integral constant overflow
Linking...
//anyway, all the same , 0 !!!

what do you expect - almost none of these numbers fit into the type
you've used, so you've invoked undefined behaviour and your compiler
is entitled to zap all your other results. .

Turn up your compiuler warning levels and read the messages.

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt>

[John Temples]

In article <do********************************@4ax.com>, Barry Schwarz wrote:

On Mon, 28 Mar 2005 14:17:49 +0900, "±èµ¿±Õ"
<na*******@game.hs.kr.NOSPAMOK> wrote:

float d = 512 * 512;

Pick an easy one, like d, and work it out in hex.

I'm not sure that d is an easy one if your expectation is that the way
the expression on the right side of the = is evaluated is influenced
by the type of the variable on the left side of the =, which is a
common misconception.

--
John W. Temples, III

[Peter Shaggy Haywood]

Groovy hepcat ±èµ¿±Õ was jivin' on Mon, 28 Mar 2005 14:17:49 +0900 in
comp.lang.c.
Why does the answer is 0?'s a cool scene! Dig it!

#include"stdio.h"
Wrong! That should be

#include <stdio.h>

[Snippage.]
long c = 256 * 256 * 256 * 256;
[More snippage.]
printf("a= %d \nb= %d \nc= %d \nd= %d \nd= %f \ne=%lf \n", a,b,c,d,d,e); ^^ ^
Has anyone pointed out this error yet? You're passing a long but
telling printf() to expect an int (%d conversion specifier).
printf("a1= %d \ne1=%lf\n",a1,e1);

^^^
In C 90 there is no %lf conversion specifier. I think (and please
correct me if I'm wrong, sombody) this is allowed by C99. But you're
not using a C99 compiler, otherwise it would have rejected your main()
because you did not specify the return type, and C99 does not have
"implicit int" as C90 did.
You should also have a return statement at the end. Portable return
values are 0, EXIT_SUCCESS and EXIT_FAILURE (the latter two being
macros defined in stdlib.h).

--

Dig the even newer still, yet more improved, sig!

http://alphalink.com.au/~phaywood/
"Ain't I'm a dog?" - Ronny Self, Ain't I'm a Dog, written by G. Sherry & W. Walker.
I know it's not "technically correct" English; but since when was rock & roll "technically correct"?

[Dave Thompson]

On Mon, 28 Mar 2005 03:46:55 -0500, do*@dot.dot wrote:

On Mon, 28 Mar 2005 14:17:49 +0900, "±èµ¿±Õ" <na*******@game.hs.kr.NOSPAMOK>
wrote:

< various integer overflows, snipped>

int a1 = 256 * 256 * 256 * 256;

Depending on your compiler, another overflow ... 256^4 = 4,294,967,296

You'd need 64 bits to hold this value. It's 1 more than can be stored in an
unsigned 32 bit variable... more than double what a signed 32bit variable
can hold.

Nit: more than 32 bits, but not necessarily 64. I don't expect to see
anyone building a 33-bit machine, although C would allow it, but there
have been 36-bit, 48-bit, and 60-bit word machines and at least some
of them have had C implementations.

- David.Thompson1 at worldnet.att.net