strcpy / strcat奇怪的字符输出

Question

I have the following piece of code for a custom String class:

const String &String::operator+(const String &right)
{
   String temp;
   temp.length = length + right.length;
   temp.sPtr = new char [temp.length + 1];
   assert( sPtr != 0 );
   strcpy(temp.sPtr, sPtr);
   strcat(temp.sPtr, right.sPtr);
   return temp;
}

where sPtr is a char* .

But, when I execute this function on two strings, I get garbage characters as a result, like this:

 ]√Hâ«Ö“x˘" = "The date is" + " August 1, 1993

I don't have the slightest clue what is happening. I've read a couple of testimonials of people who have gotten garbage characters before the resulting string is concatenated, but I don't understand at all why the entire string would be garbage characters.

Any help would be really great. Thanks in advance!

Answer 1

Don't return an object by reference that is 'temporary'. Once the function ends the temp string is de-allocated, and since the string is set to temps address it becomes garbage.