can't modify char* - Memory access violation

Question

Why does it say \"Memory access violation\"?

  char* str = \"HelloGuys\";
  int len = strlen(str);
  for (int i=0; i<(len/2); ++i){
        char t = str[l         


        

Answer 1

The behaviour is undefined if a program attempts to modify any portion of a string literal (most compiler chose to raise a "Memory access violation" error). The most important thing is to identify when you are trying to modify string literals and when you are not.

This is ok:

 char str[]  = "string literal";
 str[0] = 'S';

You have made a copy of the string literal. You are not modifying the string literal, but the array str.

This is not ok:

 char *str  = "string literal";
 str[0] = 'S';

You never made a copy of the string; the pointer is pointing to the string literal itself. You are attempting to modify the string literal.

Answer 2

To fix this, use an array instead of a pointer to read-only memory:

char str[] = "HelloGuys";   // change this line
int len = strlen(str);
for (int i=0; i<(len/2); ++i){
    char t = str[len-i-1];
    str[len-i-1] = str[i];
    str[i] = t;
}

Answer 3

As Prasoon already said, string literals are not modifiable.

If you need a modifiable array of chars have it like this:

char str[] = "HelloGuys";

Answer 4

String literals are stored in read only section of memory. Any attempt to modify the contents of a string literal invokes Undefined Behaviour (segmentation fault on most implementations).

Use an array of characters rather

char str[] = "HelloGuys";