Thread: Adding two strings into one string

Hello,
So I guess I have a problem with understanding the whole string issue in C, since i've been working on this little piece of code for a while now, trying to achieve what I want.

Here is the code. How do I add two strings (head and body) into one string and return it to the caller?

Code:

char* compose(int type){
	char *response, *head, *body;
	
	switch (type){
		case	1:{
			head=f1();
			body=f2();
			break;
		}case 2:{
                        ...
		}
                 ...
	}
	//Some code to do here - adding head and body into response
        return response;
}

The thing is that I dont know the size of the string that respose will contain (well, I know, but I try to do it differently), and so I can't declare it as a char array, and so I can't use strcat(). If I do declare it as char array, then I cant return it, because it is a local variable.
Anyone can give me a hand here?
Thanks in advance!

Originally Posted by stahta01

lookup malloc. malloc - C++ Reference

Tim S.

I don't want to use malloc(). As far as I understand, I should use malloc() when only if I need to allocate memory dynamically. Here the size of the strings is fixed.
Is there a way to do without malloc()?

You can pass an char array from the calling function. Then store the response in there so you don't need to use malloc.

So it will be like this. Just make sure that head and body will fit in response.

Code:

void compose(int type, char *response){

    char *head, *body;

     
    switch (type){
        case    1:{
            head=f1();
            body=f2();
            break;
        }case 2:{
                        ...
        }
                 ...
    }
    //Some code to do here - adding head and body into response
        return response;
}

These two statements of yours seem to be at odds:

The thing is that I dont know the size of the string that respose will contain

I don't want to use malloc(). As far as I understand, I should use malloc() when only if I need to allocate memory dynamically. Here the size of the strings is fixed.