Test Your C Skills - Errors

[pete]

char ch;
int i;

scanf("%c",&i);
scanf("%d",&ch);

After reviewing your above explanation along with the
code again I see that you are referring to the scanf statement instead
of the printf statement, however I would not say that the results are
UB. They would most certainly not be the intended results, however I
think that it would be perfectly defined.

Not defined at all.

scanf("%d",&ch) is going to treat (&ch)
as though it were the address of an int type object.
That means that scanf may write to more than one byte
when there is only one byte of memory reserved there.

 

[Sharath]

I noticed a couple of issues with Q12.11. I've pasted the original text
as-is from the site (with formatting changes and nothing more) for those
who may not have read it yet.

Q12.11

Point out the error in the following program.

#include"stdio.h"

main()
{
char ch;
int i;

scanf("%c",&i);
scanf("%d",&ch);
printf("%c%d",ch,i);
}

Erratum:

2. In the printf statement, %c is used for printing integer i, and
%d for character, this causes undefined behaviour.

No this is not [entirely] true. Printing a character as an integral type
is perfectly valid and defined in the C standard, however it may not
yield the same results intended (e.g., an integral type instead of an
ascii character).
After reviewing your above explanation along with the
code again I see that you are referring to the scanf statement instead
of the printf statement, however I would not say that the results are
UB. They would most certainly not be the intended results, however I
think that it would be perfectly defined.

Yes, I was referring to scanf statement. Thanks for pointing it out.
But it is UB for scanf statement, as pete said, it may write more
than one byte to the char object.
I have now made corrections, you can find link to the modified page is
below:
http://avsharath.googlepages.com/TestYourCSkillsErrata2.htm
-
Sharath.

 

[Old Wolf]

Below is a link to an errata list I made for the book "Test Your C
Skills" Written by Yashwant Kanetker.
http://avsharath.googlepages.com/TestYourCSkillsErrata.htm
Please let me know if I've written anything wrong there, or anything
that should be added there.

Something nobody has mentioned yet: 'erratum' is singular. When
you are presenting multiple errors the word is 'errata'.

 

[Richard Bos]

"Ben Pfaff" <[email protected]> ha scritto nel messaggio
--
int main(void){char
p[]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz.\
\n",*q="kl BIcNBFr.NKEzjwCIxNJC";int i=sizeof p/2;char *strchr();int
putchar(\
);while(*q){i+=strchr(p,*q++)-p;if(i>=(int)sizeof p)i-=sizeof
p-1;putchar(p\
);}return 0;}

The output should end with a comma, not a period.

Why?

http://en.wikipedia.org/wiki/JAPH

I'm sorry, but _Perl_ hackers are off-topic here. Ben is a _C_ hacker,
and JACH don't require the comma. That's because C hackers, unlike Perl
hackers, aren't psychotic where punctuation is concerned.

Richard

 

[Christopher Benson-Manica]

A corrected source:

^almost!

#include"stdio.h"

#include <stdio.h>