Exception/Error division in D

deadalnix deadalnix at gmail.com
Thu May 31 02:04:15 PDT 2012

Le 31/05/2012 03:06, Artur Skawina a écrit :
> On 05/31/12 00:21, Jonathan M Davis wrote:
>> Now, it's perfectly possible to design code which never checks for null
>> pointers and if a null pointer is dereferenced throws an Exception and
>> attempts to recover from it (assuming that it's possible to detect the
>> dereference and throw at that point, which AFAIK is impossible with segfaults
>> - maybe it could be done on Windows with its Access Violations, but segfaults
>> trigger a signal handler, and you're screwed at that point). But writing code
> No, it's easily recoverable. That does not mean however that it would be a good
> idea to map segfaults to exceptions as a language feature. And dereferencing a
> null pointer is *not* guaranteed to trap, all you need is a large enough offset
> and you will get silent data corruption.
>     int i = 42;
>     auto j = cast(size_t)&i;
>     ubyte* p = null;
>     p[j] = 13;
>     assert(i!=42); // oops
> artur

Most system protect at least the first page (the first 4Kb ). For other 
it is doable within druntime with page protection.

For bigger stuff, they have to be forbidden in @safe code or runtime 
check should be added.

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