On 12/31/2012 7:30 PM, Joe Pfeiffer wrote:
Jari Fredriksson <ja...@iki.fi> writes:
31.12.2012 20:33, Zbigniew Komarnicki kirjoitti:
Is this OK or is this a bug, when the wariable 'n' is
initializing by negative value? There no any warning.
Is this normal? I know that value -5 is converted
to unsigned but probably this should by printed a warning,
when this is a constant value. What do you think about this?
// prog.cpp
#include <iostream>
using namespace std;
int main()
{
const unsigned int n = -5;
cout << "The variable n is: " << n << endl;
return 0;
}
Results:
$ g++ -Wall -W prog.cpp -o prog
$ ./prog
The variable n is: 4294967291
Thank you.
This is a known bug in Debian GNU/Linux. Happy new year ;)
Where does the standard require a warning in this case? If no warning
is required, the behavior is not a bug.
I don't have a copy of the standard any more, but IIRC it does need a
warning. It requires a conversion from signed to unsigned, which can
cause incorrect data (as in this case).
Promotions (i.e. short to int, float to double) will never cause a loss
of data, and do not require warnings.
But I also admit it's been several years since I looked at the spec and
my memory isn't what it used to be (at least that's what my wife tells me).
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