Segmentation Error

This is a discussion on Segmentation Error within the C Programming forums, part of the General Programming Boards category; So I have this code that's supposed to reverse a string and upon printing of the returned result I get ...

  1. #1
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    Segmentation Error

    So I have this code that's supposed to reverse a string and upon printing of the returned result I get a segmentation error.

    Now I put in several printf statements to test and I've found that the error is caused by the strcpy function.

    I'm confused as to why this is happening, could someone tell me how I can fix it?

    Code:
    char *reverse(char *input) {
    	int i; 
    	int j = 0;
    	char *temp = calloc(100, sizeof(char));
    	for(i=strlen(input)-1; i>=0;i--) {
    		temp[j] = input[i];
    		j++;
    	    }
    	temp[j] = '\0';
    	strcpy(input, temp);
    	free(temp);
    	return input;
    }

  2. #2
    Gawking at stupidity
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    How is the space for input originally being allocated? Is it an array? malloc()'d? A string literal???
    If you understand what you're doing, you're not learning anything.

  3. #3
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    calloc'd

    Code:
    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    
    char *reverse(char *input) {
    	int i; 
    	int j = 0;
    	char *temp = calloc(100, sizeof(char));
    	for(i=strlen(input)-1; i>=0;i--) {
    		temp[j] = input[i];
    		j++;
    	    }
    	temp[j] = '\0';
    	strcpy(input, temp);
    	free(temp);
    	return input;
    }
    
    
    int main(void) {
      char *rstring = calloc(100, sizeof(char));
    
    
    
    strcpy (rstring, reverse("hello."));
    
    
    /*	printf( "%s\n", rstring ) ; */
    	return 0;
    }

  4. #4
    DESTINY BEN10's Avatar
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    "hello" is a string literal, which can only be read but you're trying to modify it in the strcpy(input,temp); statement. The solution would be to malloc input before strcpy in the reverse function.
    Last edited by BEN10; 12-05-2009 at 09:58 PM.
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  5. #5
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    Okay, that helped, thanks.
    Last edited by mrdibby; 12-06-2009 at 05:10 AM.

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