error: lvalue required in while ((arg_to)++ = (arg_from)++);

Asked Jan 19 '18 at 04:44

Active Jan 19 '18 at 04:44

Viewed 37 times

arg_to and arg_from are of type char*

Why does the first expression work properly whereas the second one throws the following error:

error: lvalue required as left operand of assignment

asked Jan 19 '18 at 04:44

Aquarius_Girl

3

Because `((*arg_to)++)` is not an lvalue. It's like you're saying `x + 2 = 3`. – Raymond Chen Jan 19 '18 at 04:50
1

May I convince you, "Don't border. Just never write this kind of thing."? – Jan 19 '18 at 05:19
@RaymondChen Why is that not considered lvalue? Please explain in an answer. – Aquarius_Girl Jan 19 '18 at 05:21
1

The postfix operator returns the old value. If it were returning the object itself, you'd get the incremented version. – chris Jan 19 '18 at 05:29

error: lvalue required in while ((*arg_to)++ = (*arg_from)++);