warning: operation on 'zero' may be undefined

[Giovanni Bajo]

Paul Brook wrote:

>> foo.cxx: In function `int main()':
>> foo.cxx:4: warning: operation on 'zero' may be undefined
>> 
>> What does this mean ?
> 
> You incrementing and assigning to the same variable in one statement,
> which invokes undefined behaviour.
> 
> The code you wrote can be interpreted as
> zero = zero%3;
> or
> zero = (zero % 3) + 1
> or possibly even something entirely different.

The error message could use a clarification though.

Giovanni Bajo