The same expression on both sides: x - !!x

[Martin Poupě]

Hello,
lets' have following routine:

unsigned one_lower_if_nonzero(unsigned x)
{
    return x - !!x;
}

It should (obviously) return (x - 1) for x positive, zero for x == 0.
But cppcheck (online demo) complains: [test.cpp:3]: (style) Finding the same expression on both sides of an operator is suspicious and might indicate a cut and paste or logic error. Please examine this code carefully to determine if it is correct.
Cppcheck 2.11 on my project says: style: Same expression on both sides of '-'. [duplicateExpression]
I think cppcheck overlooks the double negation "!!".
Best Regards Martin

[CHR]

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/11820