DIP1028 - Rationale for accepting as is

[Zoadian]

On Monday, 25 May 2020 at 09:25:52 UTC, Johannes T wrote:
> On Monday, 25 May 2020 at 00:56:04 UTC, Timon Gehr wrote:
>> [..]
>
> After thinking about it, Walter ultimately made the right 
> decision, leading to overall higher safety and code quality.
> We all agree that making extern C @safe is incorrect. It's also 
> meaningless. Even if you were to verify the safety of a 
> specific version of your binding, it can't be known what's 
> loaded at runtime. It's not the compiler's concern. @safe 
> extern shall be an error. We might additionally make an 
> exception and make all extern C @system. It would be correct 
> for the declarations, but inconsistent in regard to default 
> safety. It doesn't affect the outcome. Let's say we'll go with 
> @system, it gives us a bit more freedom.
> We hit compile, our now safe wrappers are errors. We are most 
> likely to do one of two things, depending on the module failing 
> to compile. If it mostly wrappers, we slap @trusted: at the 
> top. If there are just a few functions calling C, we only 
> annotate those with @trusted. Let's be real, we probably won't 
> begin checking and annotating the trustworthiness of the C 
> functions. An individual programmer might, but not on average.
> We are formally correct, but @trusted can't be trusted at this 
> point. It has lost its meaning. We now have to check all 
> foreign @trusted code, which we probably won't.
> We could have moved the problem one level down and slapped 
> @trusted: on top of the @system declarations. Now there is a 
> bunch of safe code using them. It doesn't change much. 
> @trusted: is easier to grep, but we won't put everything down 
> and begin trustworthily annotate extern C. So yeah, I do 
> believe Walter was right. @safe on extern is formally incorrect 
> but leads to safer code because @trusted still has its power.

you complain about @trusted losing it's meaning, but @safe was 
ment to mean "mechanically verified memory safety". it should be 
forbidden to add @safe to any function that can not be verified 
by the compiler.

the compiler should do it's best to alert you of any mistakes you 
might make.
if the compiler does silently add @safe or @trusted to extern(C) 
functions you are are to miss annotating it. that is a bad thing 
for everyone that actually cares about safety.

you can't prevent programmers from doing stupid things. but you 
can at least warn them.