Thread: Segmentation faults when trying to modify a character array

  1. #1
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    Unhappy Segmentation faults when trying to modify a character array

    Hello

    I've initialized a character array in my main, and passed it onto one of my functions convertToPostfix(char infix[], char postfix[]). It isn't a constant read only array (constant char*) ive explicitly initialized it to char postfix[] = "";



    Code:
    if ((nextChar > 47) && (nextChar < 58)){    //if its a digit
            postfix[++postfixIndex] = nextChar;
            while (infix[i + 1] > 47 && infix[i + 1] < 58){
                nextChar = infix[++i];
                postfix[++postfixIndex]=nextChar;//segmentation fault when assigning from infix to postfix**
                            }
    please explain what I'm doing wrong....D:

  2. #2
    and the hat of int overfl Salem's Avatar
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    > It isn't a constant read only array (constant char*) ive explicitly initialized it to char postfix[] = "";
    In which case, it is an array with length 1
    So my guess is you overwrote the end.

    Perhaps
    char postfix[100] = "";
    or some other suitable number for the maximum amount of storage you need.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  3. #3
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    i've done that, but nonetheless, I cannot modify it outside of my main, even when explicitly passing it onto another function. and as far as i know, whenever you pass an array down by parameters, it is an automatic call by reference, ergo, why can it not access it?

    i've ended up making a char * in my function to navigate through the indecies and it works. how come it can modify my infix array, but not my postfix? what the heck!?

  4. #4
    and the hat of int overfl Salem's Avatar
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    You should post the whole code, if you want a better diagnosis of a segfault.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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