Re: Error in the "strcat" function

[Guy Harris <guy () alum mit edu>]

Adelmo Silva wrote:
> Jin YunYe wrote:
> > On 2/2/07, Adelmo Silva <adelmojs () hotmail com> wrote:
> > > Hello,
> > > I have a error:
> > >
> > > debian:/home/adelmojs/MONOGRAFIA# gcc teste1.c -lpcap -o teste1
> > > teste1.c: In function 'SNIFFER':
> > > teste1.c:294: warning: passing argument 2 of 'strcat' makes pointer from
> > > integer without a cast
> > > teste1.c:294: error: incompatible types in assignment
> > >
> > > THE LINE 294 HAS:
> > > string1 = strcat(string1,ips1[i]);
> >
> > Could you quote the line where you declare "string1" and "ips1" in 
> > your program?
>
> char string1[15], string2[15];
>
> u_char flag, *ips1, *ipd1, *ips2, *ipd2;

That means ips1[i] is a u_char, which is an (unsigned) integer.

If you mean that you want to copy the text starting at the "i"th 
character in ips1 (where the first character is the 0th character), you 
want to do

        strcat(string1, &ips1[i]);

because

        1) you want a *pointer* to the text starting at the "i"th character in ips1

and

	2) you can't assign anything to string1, as it's an array, not a 
pointer (arrays are *NOT* pointers in C, although a reference to an 
array, in most but *NOT* all contexts, is converted to a pointer to the 
element of the array).

Note also that string1 doesn't get any bigger, as an array, so if its 
contents are "0123456789", ips1's contents are 
"abcdefghijklmnopqrstuvwxyz", and i is 5, you will overflow the string1 
array.

(Note that none of this has anything to do with libpcap.)
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