On Tue, May 06, 2014 at 01:06:14AM -0700, Jonathan M Davis via
Digitalmars-d-learn wrote:
> On Mon, 05 May 2014 22:16:58 -0400
> Nick Sabalausky via Digitalmars-d-learn
> <digitalmars-d-learn@puremagic.com> wrote:
>
> > On 5/5/2014 10:11 PM, Nick Sabalausky wrote:
> > > Is this kinds stuff a sane thing to do, or does it just work by
> > > accident?:
> > >
> > > void modify(ubyte[] dynamicArr)
> > > {
> > > dynamicArr[$-1] = 5;
> > > }
> > >
> > > void main()
> > > {
> > > ubyte[4] staticArr = [1,1,1,1];
> > > modify(staticArr);
> > > assert(staticArr == [1,1,1,5]);
> > > }
> >
> > Duh, it's just using a normal slice of the static array...
> >
> > // Roughly:
> > dynamicArr.ptr = &staticArr;
> > dynamicArr.length = typeof(staticArr).sizeof;
> >
> > So all is well, and deliberately so. Pardon the noise.
>
> It's definitely deliberate, though I think that it's a flaw in the
> language's design. IMHO, static arrays should never be automatically
> sliced, but unfortunately, changing that would break too much code at
> this point. The biggest problem is the fact that it's inherently
> unsafe, though unfortunately, the compiler currently considers it
> @safe:
>
> https://issues.dlang.org/show_bug.cgi?id=8838
[...]
A particularly pernicious instance of this hole is the following:
class C {
int[] data;
this(int[] args...) @safe {
data = args;
}
}
C f() @safe {
return new C(1,2,3);
}
void main() {
import std.stdio;
writeln(f().data); // on my system, writes garbage
}
Exercise for the reader: spot the bug.
T
--
English has the lovely word "defenestrate", meaning "to execute by
throwing someone out a window", or more recently "to remove Windows from
a computer and replace it with something useful". :-) -- John Cowan
