> 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
This is expected behavior, but not defined by the standard because the result
is not portable. That is, a rollover value will occur, but it could vary
depending on the width of an int, and possibly by the binary representation.
As far as I know all systems that Debian with gcc runs on are two's complement,
but still...
I cannot speak to the C++11 standard because ISO/ANSI are not asking a
reasonable price for the specification docs, and I can't afford the price.
A good compiler *may* warn you about this, but it may not do so by default.
You may have to turn the warnings on. Note: gcc's -Wall is tricky. You may
still not get what you expect.
This kind of type shenanigan is allowed in C/C++ because of silent standard
conversions. A strongly-(enough)-typed language will not permit conversions to
or from signed<->unsigned without a cast or a conversion function. C/C++
allows this because there is no loss of significant digits (precision).
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