Problems with string reverse implementation

Question

Possible Duplicate:
Why is this C code causing a segmentation fault?

I am writing a simple string reverse script.

I added print statements to debug. I keep getting a run time exception before Error1. But I can't seem to figure out the reason.

Here's my code:

#include <iostream>
#include <cstdlib>

using namespace std;

int strlen(char* s){ 
  int i = 0;
  while(*s != '\0'){
    i++;
    s++;
  }
  return i;
}

void reverse(char* src){

  char* dest = src+strlen(src)-1;
  char temp;

  while(src < dest){
    temp = *src;
    cout << "Error0" << endl;
    *src = *dest;
    cout << "Error1" << endl;
    *dest = temp;
    cout << "Error2" << endl;
    src++;
    dest--;
  }

}

int main (void){

  char* s = "Hello world";
  cout << s << endl;
  int i = strlen(s);
  cout << i << endl;
  reverse(s);
  cout << s << endl;

  getchar();
  return 0;
}

Here's my output:

            Hello world
            11
            Error0

A string literal is not a `char*`, but because of old C details, compilers have to accept that anyway. Use `const char*` for any string literal, or you can initialize a `char s[]` array from a literal. — aschepler, Dec 11 '12 at 00:47
Same question, same function, same error [Why is this C code causing a segmentation fault?](http://stackoverflow.com/questions/1614723/why-is-this-c-code-causing-a-segmentation-fault) — AnT stands with Russia, Dec 11 '12 at 00:58

score 3 · Accepted Answer · answered Dec 11 '12 at 00:47

3

this

char* s = "Hello world";

needs to be

char s[] = "Hello world";

Your orignal is trying to change constant memory that you aren't allowed to change, so you need to allocate space and initialize it with the string

answered Dec 11 '12 at 00:47

Keith Nicholas

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Problems with string reverse implementation

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