Walter Bright wrote:
Fawzi Mohamed wrote:
one could argue that the unsafe operation is memset.
That's right.
The compiler always initializes a struct, so that what you describe
should never happen in a safe program.
Right.
Still as you say the following example that might indeed considered a
bug:
S s1=void,s2=void;
s1.s=0; s1.d=0;
s2.s=0; s2.d=0;
assert(s1 == s2);
here the assert might fail depending on the previous content of the
memory.
I am not sure of what is the best solution, I am not sure that
defining a special comparison operation by default for each struct is
the correct solution (it can be quite some bloat), please note that a
user defined comparison function will not have these problems.
No, it's not a bug in the language, it's a bug in the user code. Using
=void is an advanced feature, and it requires the user to know what he's
doing with it. That's why it isn't allowed in safe mode.
Still I agree that traking down a bug due to this might be very ugly...
The idea with =void initializations is that they are findable using
grep, and so can be singled out for special attention when there is a
problem.
The same issue can arise with unions. This one is pretty hard to grep for:
-----------
struct S { // 16 bytes, with a hole
ushort s;
double d;
}
union U {
char [16] c;
S s;
}
void main() {
U u;
u.c[]='2';
S a = S(5, 2.0);
u.s.s = a.s;
u.s.d = a.d;
S b = u.s;
assert( a == b);
}
