Why am I getting an access violation exception in a pointer operation?

I'm using C++ Visual Studio .Net 4.0 on Windows 7.0 x64. This happens just on the first loop of the while statement.

int main()
开发者_StackOverflow中文版{
  char *string = new char[11];

  string = "characters\0";

  toUppercase(string);

  return 0;
}



void toUppercase(char *stringPtr)
{
 while(*stringPtr != '\0')
 {
    if(*stringPtr >= 'a' && *stringPtr <= 'z')
    {
        *stringPtr = *stringPtr - 32; // this is the culprit
    }

    ++stringPtr;    
 }
}

I suspect you're doing something like this:

toUppercase("test");

The problem is "test" is an array of const char, not char, so cannot be modified. However, due to a terribly stupid deprecated special conversion, a string literal can be treated as char* anyway.

(Your function also fails to test for toUppercase(0).)

You can get #AV if memory isn't writeable:

toUppercase((char*)"str");

My guess would be that you are passing to that function a pointer to a string that resides in read-only memory. However, you would need to share the surrounding code -- i.e., how you actually call this method -- to pinpoint the problem.

EDIT: In view of the above, here's one way to get this working:

char* str = strdup("hello world");
toUppercase(str);