On 27/08/2019 14:55, Jonathan Wakely wrote:
On Tue, 27 Aug 2019 at 14:48, Jonny Grant <jg@xxxxxxxx> wrote:
On 27/08/2019 13:42, Jonathan Wakely wrote:
On Fri, 9 Aug 2019 at 21:32, Jonny Grant wrote:
Hi
Looks like the bool can't be converted to size_t
Of course it can. You're using options which enable some noisy
warnings and then turn those warnings into errors. But your example
doesn't try to conbert bool to size_t anyway, it performs arithmetic
on bools, which produces an int, then tries to convert that to size_t.
Obviously converting int to size_t changes from signed to unsigned,
and that's why you get a -Wsign-conversion diagnostic.
Questionable code (like performing arithmetic on bool values) will
often trigger noisy warnings that have many false positives. There's a
reason -Wsign-conversion isn't included in -Wall or -Wextra.
It's easy to avoid the warning if you really need to perform arithmetic on bool:
size_t i = size_t(a + b);
or:
size_t i = size_t(a) + b;
I see. I had been expected the bool to be treated as an unsigned number,
It *is* treated as an unsigned number. But C and C++ have a rule
called integer promotion which affects this. Operands smaller than
'int' will be promoted to 'int', so adding two bools is equivalent to
int(a) + int(b). Obviously that is a signed type now.
See https://en.cppreference.com/w/cpp/language/implicit_conversion#Integral_promotion
Ok, I see. Thank you for the link.
Jonny
