all OS functions should be "nothrow @trusted @nogc"

[Moritz Maxeiner via Digitalmars-d]

On Tuesday, 1 August 2017 at 21:59:46 UTC, Steven Schveighoffer 
wrote:
> On 8/1/17 5:54 PM, Moritz Maxeiner wrote:
>> On Tuesday, 1 August 2017 at 20:39:35 UTC, Marco Leise wrote:
>>> Am Tue, 1 Aug 2017 10:50:59 -0700
>>> schrieb "H. S. Teoh via Digitalmars-d"
>>> <digitalmars-d at puremagic.com>:
>>>
>>>> On Tue, Aug 01, 2017 at 05:12:38PM +0000, w0rp via 
>>>> Digitalmars-d wrote:
>>>> > Direct OS function calls should probably all be treated as
>>>> > >
>>>> unsafe, except for rare cases where the behaviour is very > 
>>>> well defined in standards and in actual implementations to > 
>>>> be safe. The way to get safe functions for OS functionality
>>>> > is to write wrapper functions in D which prohibit unsafe >
>>>> calls.
>>>>
>>>> +1.
>>>
>>> I think I got it now!
>>>
>>>     size_t strlen_safe(in char[] str) @trusted
>>>     {
>>>         foreach (c; str)
>>>             if (!c)
>>>                 return strlen(str.ptr);
>>>         return str.length;
>>>     }
>>>
>>>   :o)
>> 
>> I know this is in jest, but since `strlen`'s interface is 
>> inherently unsafe, yes, the only way to make calling it @safe 
>> happens to also solve what `strlen` is supposed to solve.
>> To me the consequence of this would be to not use `strlen` (or 
>> any other C function where checking the arguments for @safety 
>> solves a superset of what the C function solves) from D.
>> I don't think this applies to most OS functions, though, just 
>> to (OS independent) libc functions.
>
> I think it goes without saying that some functions just 
> shouldn't be marked @safe or @trusted. strlen is one of those.
>

Of course, though I think this (sub) context was more about 
writing @safe D wrappers for @system C functions than about which 
C functions to mark as @trusted/@safe. `strnlen` shouldn't be 
marked @safe/@trusted, either, but writing a @safe D wrapper for 
it doesn't involve doing in D what `strnlen` is supposed to do:

---
size_t strnlen_safe(in char[] str)
{
     return strnlen(&str[0], str.length);
}
---

Not that there's much of a reason to do so, anyway, when the D 
idiomatic way is just a Phobos away:

---
import std.algorithm;
// I probably wouldn't even define this but use the body as is
auto strnlen_safe(in char[] str)
{
     return countUntil(cast(ubyte[]) str, '\0');
}
---