On Thursday, 17 October 2013 at 22:56:04 UTC, DDD wrote:
Hi I heard that you can pass a command line argument to make D
safe. Like 0 chance of memory corruption and such. I tried
looking here http://dlang.org/dmd-linux.html but I couldn't
figure it out. If it matters I'm on windows using the latest
until a new version came out ~3weeks ago
Safe code in D is defective feature and claims that D's code can
be memory safe is the biggest misconception!
First of all, @safe is broken, which means there are many cases
when code should be rejected, but actually isn't, secondly it is
misdesigned. Root of the issue is that in D static type system
and memory safity are separated from each other. Key idea is that
having information about static type of object is not sufficient
to know whether using it is memory safe or not.
@safe foo(int[] arr) {}
void main @safe()
{
int [3] x;
// auto dg = { return x; } ;
foo(x[]);
}
This a nice case to show @safe problems. First of all, passing
static array to dynamic is of relative safety: if slice doesn't
escape, this is fine, if is does, this can be still fine if it
later for example is appended (or any operation is performed
which does not access any elements). Otherwise it is a memory
bug. In a presence of separate compilation this is impossible to
know. In such cases memory safety is at best undefined. Other
issue here is that if delegate declaration is uncommented, then
code is always memory safe because array will be allocated on
heap. However, by @safe definition code will be still rejected,
because @safe is defined in notion of static type rather than
memory type. Last issue here is that implementation is buggy and
does not reject the code in accordance with its buggy spec.
And at last, there are cases in the language which are not
covered by @safe spec, but which still produce memory errors.
So, what actually D has, is a feature, which does not really
prevents memory errors, but bans some language features and
criteria for banning features is wrong: some legal cases are
banned, some cases which should be blocked, are not. If you are
really interested in safety you can put our attention to
languages like C#. D doesn't provide such facilities.
