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conflicting types for built-in function

This is a discussion on conflicting types for built-in function within the C Programming forums, part of the General Programming Boards category; Im getting this error over my function prototype in the code below: Code: #include <stdio.h> void strcat(char s[], char t[]); ...

  1. #1
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    conflicting types for built-in function

    Im getting this error over my function prototype in the code below:

    Code:
    #include <stdio.h>
    
    void strcat(char s[], char t[]); /* error here */
    
    int main(void)
    {
    	char s[4] = {"abcd"};
    	char t[9] = {"abcdefgh"};
    
    	(strcat(s, t));
    
    	return 0;
    
    }
    
    void strcat(char s[], char t[]){
    	char match;
    	int i, j, x, q;
    	i = j = x = q = 0;
    	while(s[i] != '\0')
    		i++;
    	while(s[j] != '\0')
    		j++;
    	while(q <= i){
    	for(x = 0; x <= j; x++)
    		if(s[q] == t[x]){
    			match = 1;
    	}
    		else{
    			match = 0;
    	if(match == 1){
    		++q;
    	}
    	else{
    		t[j++] = s[q++];
    	}
    
    		}
    	}
    
    	int v = 0;
    	while(t[v] != '\0'){
    		putchar(t[v]);
    				v++;
    	}
    
    }

    Any ideas as to where im going wrong?

  2. #2
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    There is a standard function called strcat with the following declaration: char *strcat(char *dest, const char *src);. Try naming your function my_strcat or some such.

    EDIT: Unless this is a purely academic exercise, there is no reason to reinvent the wheel.

  3. #3
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    Sweet. Thats solved that problem! Thanks!

  4. #4
    Algorithm Dissector iMalc's Avatar
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    Note that your code is wrong anyway. You're first off trying to put 5 characters('a','b','c','d','\0') into an array of 4 characters. Then after that you are trying to put even more chars into one of your buffers, causing yet more overflow.
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  5. #5
    and the hat of wrongness Salem's Avatar
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    Code:
    char s[4] = {"abcd"};
    You should note that this particular string does NOT have a \0 at the end.

    Normally, the safe thing to do is omit the size and let the compiler work it out.
    Code:
    char s[] = "abcd";
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  6. #6
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    Thanks for the heads up guys! Wasn't aware that I could leave the array size initialisation to the compiler in this context! Have altered the code as you suggested. Cheers

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