0 insted of '\0' in char ptr

[sathya]

I have come across the following code which treys to implement the
strcat function. It may
be wrong or correct, but it is using integer zero instead of
appending the C string terminator '\0'.

#include <stdarg.h>
char *xstrcat(char *des, char *src, ...)
{

char *destination = des;
va_list v;
va_start(v, src);
while (src != 0)
{

while (*src != 0)

*des++ = *src++;

src = va_arg(v, char *);

}

*des = 0;
va_end(v);
return destination;
}

Is the above code is UB? Please explain.

--
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A.Alekhine
Mail to:
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[Richard Bos]

sathya <sa****@nomail.com> wrote:

I have come across the following code which treys to implement the
strcat function. It may
be wrong or correct, but it is using integer zero instead of
appending the C string terminator '\0'.

That's quite correct. '\0' _is_ an int zero; character constants have
type int, for historical reasons. The necessary conversion to char type
will be done automatically; the process should be identical regardless
of whether you spell the int zero 0 or '\0'.

Richard

[CBFalconer]

sathya wrote:

I have come across the following code which treys to implement the
strcat function. It may be wrong or correct, but it is using
integer zero instead of appending the C string terminator '\0'.

#include <stdarg.h>
char *xstrcat(char *des, char *src, ...)
{
char *destination = des;
va_list v;
va_start(v, src);
while (src != 0)
{
while (*src != 0)
*des++ = *src++;
src = va_arg(v, char *);
}
*des = 0;
va_end(v);
return destination;
}

Is the above code is UB? Please explain.

No it isn't for that reason. However it is a horror and an error
prone trap, as is almost any variadic function in C. You would be
better off using the FreeBSD originated strlcat and strlcpy
routines, for which you can find an implementation at:

<http://cbfalconer.home.att.net/download/>

--
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Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net> USE worldnet address!

[Herbert Rosenau]

On Tue, 14 Dec 2004 12:14:26 UTC, sathya <sa****@nomail.com> wrote:

I have come across the following code which treys to implement the
strcat function. It may
be wrong or correct, but it is using integer zero instead of
appending the C string terminator '\0'.

'\0' is commonly used to document inline that you means a (char)0.
0, char(0), '\0' have always the same meaning but

0 requires from the reader to see that you assigns/compares a char.
The reader has to think an extra step to see that you means a char.

char(0): casting is always an dangerous option, requiring rethinking
it if it does really what you needs and means, so avoiding casts
whenever possible makes the code more readable.

'\0' is documenting that you speaks about chars, not ints. It is more
for the reader than for the compiler.

So both, 0 and '\0' are commonly used to address a null value as char,
whereas '\0' is more documentative but costs 3 extra typings. C
programmers are often sluggish, so they avoid typing as they can.

--
Tschau/Bye
Herbert

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[Richard Bos]

"Herbert Rosenau" <os****@pc-rosenau.de> wrote:

On Tue, 14 Dec 2004 12:14:26 UTC, sathya <sa****@nomail.com> wrote:

I have come across the following code which treys to implement the
strcat function. It may
be wrong or correct, but it is using integer zero instead of
appending the C string terminator '\0'.

'\0' is commonly used to document inline that you means a (char)0.
0, char(0), '\0' have always the same meaning but

No, they don't; 0 has not just exactly the same meaning, but also the
same type, as '\0', but char(0) is a syntax error (and (char)0, which
you might have meant, has the same value, but a different type).

Richard