strcat() error with gcc
 

Hi friends

I have one particular problem with this following short code written in C

#include<stdio.h>
#include<string.h>

int main()
{
printf("%s",strcat("Hello","World");
return 0;
}

I m getting the error as segmentation fault.

If I run the same code in Tourbo C or Borland C, it works fine.

Please help me what is the problem with this code or where i have gone wrong.

maybe it is this parethesis:

printf("%s",strcat("Hello","World"));

anyway thats asyntax error...

yeh.. sorry

it was typing mistake..

I am getting segmentation fault

The erronious program is as follows

#include<stdio.h>
#include<string.h>

int main()
{
printf("%s",strcat("Hello","World"));
return 0;
}

giving segmentation fault

Does it work if you explicitly 0-terminate the strings? ( printf("%s",strcat("Hello\0","World\0")); )

No ..

Still it is giving the same error.

The thing is that the above code works properly under Turbo and Borland compilers

Ah, silly me, should have RTFM before answering. Of course it's
char *strcat( char *strDestination, const char *strSource ),
therefore you're writing the result into the memory reserved for "Hello". The code should rather look like

#define PLENTY_OF_BYTES 32
char szresult[PLENTY_OF_BYTES];
szresult[0]=0;
strcat(szresult,"Hello");
strcat(szresult," World");

hi

that I can understand..

but why the same code works in borland compiler and tourbo compiler why not in gcc ..!!!!!

Any clue abt this ?

Because gcc stores string literals in read-only memory. The same program will probably work if you compile it with gcc -fwritable-strings prog.c -o prog althought you'll have undefined results.

thanks..atlease we able to remove the segmentation fault.

yes..

it is not giving error like segmentation fault.

But it is giving only the part of the appended string. In the above example code it gives the output

orld

It means , it is missing the first character of second (source)string and not showing first string i.e destination .

You can try in your PC also...!

Why it is like this? Can anybody guide me ?

Because the only correct way to use strcat() is the way Marius2 showed you.

gcc is correct, string literals are null-terminated and of type and they live throughout the lifetime of the program. Writing to one yields undefined results. If a "lesser" compiler happens to accept it without bombing out it's still not something one should rely on. And if you're thinking of using -fwritable-strings option I can inform you that's it's being removed in the upcoming 4.0 version of gcc. So what you want is is what Marius2 showed. Just remember to check if the destination has room for the source (including the \0) or you will get in trouble.

Ohh god that code makes my brain cry

using strcat like this should be banned :P

Hi friends

there is a food for thought...!

To my knowledge,

strcat("Hello","World");

returning the pointer to string..am i right ?

For example, the below code works properly where p is the pointer to string.

int main()
{
char *p="Suresh";
printf("%s",p);
return 0;
}

why not in the first code or what is the difference between two approach.

awaiting your reply.

Here's a way to code your own strcat() function:
As you might be able to see, the string in the first parameter gets modified. Which means you can never pass a string literal as the first parameter to strcat() because string literals are stored in read-only memory. You can't modify read-only memory.

Here's a sample program that uses mystrcat() and will work the exact same way with C's strcat():
I don't know how to explain it any better than that.