NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/1174

Internet Message Format | 1996-08-05 | 1.6 KB

Path: crl.crl.com!not-for-mail
From: [e-mail] (Robert Fry)
Newsgroups: comp.lang.c
Subject: Re: Strcat Doesn't work for this?
Date: 11 Jan 1996 15:22:10 -0800
Organization: CRL Dialup Internet Access
Message-ID: <4d4632$[e-mail]>
References: <[e-mail]>
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** Craig Cook ** <[e-mail]> writes:

>Here is my excerpt of code in question:

>Putword(int w, char *imageChar)
>{
>        w = (w & 0xff);
>        strcat( imageChar, (const char *)w );
>}

>Why does it core dump?  It should work right?

Actually, no it shouldn't. Strcat is expecting two pointers to character,
and you are passing it a pointer and a single byte that has been cast to
a pointer. In actual fact, your second parameter has now become a pointer
with a value ranging from 0-255.

Remember, this second parameter should be a string. That is, a sequence
of bytes terminated by a NULL. Assuming you're on a little-endian machine
(which you appear to be doing -- it's /far/ from guaranteed!), if you
change the call to strcat to look like: strcat( imageChar, (const char *)&w);
then this code should append the low-order byte of w to the imageChar string.

I think most people would consider this to be poorly-written, however. It
invokes hardware-dependent behavior as well as only writing one byte, not
a word on the off chance it DOES work. If you have to perform this
operation, memcpy is probably a better way to do it -- or simply do the
appropriate mask-and-shift operations to copy to the appropriate position
in imageChar.