Reverse a c-type string.

Question

Here is my code:

    void reverseStr(char *str)
{
    if (str == NULL) return;
    int i=0, j=strlen(str) -1;
    while(i<j)
    {
        char temp = str[j];  //i think this is the cause of the problem
        str[j] = str[i];
        str[i] = temp;
        i++;
        j--;
    }
}

So here is where it is called:

int main()
{   
    char *str = "Forest Gump";
    reverseStr(str);
    cout << str;
}

Here is my error: /Applications/TextMate.app/Contents/SharedSupport/Bundles/C.tmbundle/Support/bin/bootstrap.sh: line 7: 1931 Bus error "$3".out

Any thoughts? Thanks in advance.

Answer 1

String literals are read only memory, you can't reverse them, nor modify them in any way without encountering undefined behavior.

Copy your string into a buffer first, then pass in the buffer. Or declare an array instead of a pointer and initialize that array with a string initializer.

Answer 2

The error is in a bash/shell script not in your program. Would you please post the bash script also?

Answer 3

Str pointes to a fixed string. You are modifying it in place. In other words, you trying to change the text literal. Try this:

char *str = strdup("Forest Gump"); 
reverseStr(str); 
cout << str; 
free(str);