Zcoin implementation bug enabled attacker to create 548, 000 Zcoins

[ketmar via Digitalmars-d]

Walter Bright wrote:

> https://makebitcoingreatagain.wordpress.com/2017/02/18/is-the-zcoin-bug-in-checktransaction/#update6
>
> The error is here:
>
> https://github.com/zcoinofficial/zcoin/blob/81a667867b5d8489...
>
> and the line of code:
>
> zccoinSpend.denomination == libzerocoin::ZQ_LOVELACE;
>
> In other words, a statement with no effect. In D, such a line gives an 
> error, not a warning:
>
> Error: == has no effect in expression

only for primitive types, sadly.

  void main () {
    Object a, b;
    a == b;
  }

oops. no more error messages. yes, i know that this invokes `opEquals()`, 
and `opEquals()` can have side-effects. but what are the chances of writing 
such code *intentionally*?

i guess, compiler should emit error for *any* usage of "==" without using 
the result, even if it lowers to `opEquals()` or something. and if one 
really want to use it and drop it's result, there is always escape path:

  cast(void)(a == b);