random c++ question thingy

[Dragon45]

void strcpy(char *fin, char *src)
{
while (*src) {
*fin++ = *src++;
}
*fin = '\0';
}

The above code is supposed to copy one string to another; however, im wondering about two things:

1) The src incrementation will work like

*(src++) is assigned to *(fin++);
(Why?) wouldn't the first character be skipped entirely?

2) I recognize that the while loop's condition means that the loop will continue until *src points to "null"/uninit'ed data (essentially until the string ends). However, we're explicitly assign \0 (null-termination character) to the last value of *fin.

If \0 counts as null in a boolean statement then the *fin pointer will never be incremented the last time, and the last non-null char will be overwritten.

If \0 does not count as null in a boolean statement, then things might work out, but the last \0 will still be overwritten (making the \0 completely superfluous).

------------------

So I guess I'm missing something here. Anyone care to enlighten me?

[lurker]

Note that the ++ comes after the variable name. It's a post-increment, so it's not done until the statement is over. That should directly answer #1, and it also answers #2 indirectly: when src points to a null character for the while check, that null character has not been copied yet, and fin has already been updated to the spot where the new null should be stored.

[KDR_11k]

x++ is a post increment, it returns the value x had before being incremented. This also means that once *src is \0 the loop doesn't get executed again so the \0 does not get copied.

[rattle]

Code: Select all

void strcpy(char *fin, char *src)
{
	while (*src) *++fin = *++src;
	*fin = '\0';
}

?

If your IDE is half-decent you can setup a watch to see what value src and fin have.